IoT Glossary: 100+ Internet of Things Terms & Definitions (2026 Guide)

A

ADC (Analog-to-Digital Converter)

Converts analog voltage signals (like from a temperature sensor or potentiometer) into digital numbers that a microcontroller can read. ESP32 has 18 ADC pins (12-bit resolution, 0-4095).

💡 Example: Reading a potentiometer value with analogRead(pin);

API (Application Programming Interface)

A set of rules that allows different software applications to communicate. In IoT, APIs let your devices send data to cloud platforms or receive commands from mobile apps.

💡 Example: OceanRemote's REST API allows you to control devices from any programming language.

Arduino IDE

The most popular programming environment for ESP32, ESP8266, and Arduino boards. Free, open-source, and supports thousands of libraries.

💡 Example: Where you write, compile, and upload code to your ESP32.

AWS IoT (Amazon Web Services IoT)

Amazon's cloud platform for IoT devices. Offers device management, data processing, and integration with other AWS services. Popular for enterprise IoT solutions.

B

BLE (Bluetooth Low Energy)

A power-efficient version of Bluetooth designed for IoT devices that run on batteries. ESP32 supports BLE, making it perfect for battery-powered sensors and wearables.

💡 Example: A door sensor that runs for months on a coin cell battery using BLE.

BME280

A popular sensor that measures temperature, humidity, and barometric pressure. Often used in weather stations and altitude tracking.

💡 Example: Creating a weather station that predicts rain based on pressure changes.

Brownout

When voltage drops below the minimum required for operation. ESP32 has a brownout detector that triggers a reset when voltage falls below ~2.9V.

💡 Example: "Brownout detector was triggered" error message – usually means your power supply is inadequate.

Baud Rate

The speed of serial communication, measured in bits per second. Common rates: 9600, 115200, 230400. Must match between ESP32 and Serial Monitor.

💡 Example: Serial.begin(115200); sets communication speed to 115200 baud.

C

Cloud

Remote servers that store, process, and manage IoT data. OceanRemote provides cloud infrastructure so you don't need your own servers.

CoAP (Constrained Application Protocol)

A lightweight protocol designed for constrained IoT devices. Similar to HTTP but optimized for low-power, low-bandwidth networks.

Current Draw

The amount of electrical current a device consumes, measured in milliamps (mA). ESP32 draws 80-240mA, ESP8266 draws 70-170mA.

💡 Example: ESP32 in deep sleep draws only 5-150µA – great for battery projects!

Cron Job

A scheduled task that runs automatically at specified times. Used in IoT for periodic data collection, cleanup operations, or sending reports.

D

DAC (Digital-to-Analog Converter)

Converts digital numbers into analog voltage. ESP32 has 2 DAC pins (GPIO 25 and 26) that can output 0-3.3V.

💡 Example: Generating audio signals or controlling analog devices like servo motors.

Dashboard

A visual interface that displays real-time data from your IoT devices. OceanRemote provides customizable dashboards for monitoring sensors and controlling relays.

Deep Sleep

A low-power mode where the ESP32 turns off most of its components, drawing only 5-150µA. Wakes up via timer or external trigger.

💡 Example: A weather sensor that wakes every 10 minutes to send data, then goes back to sleep.

DHT22

Popular temperature and humidity sensor. Accuracy: ±0.5°C / ±2% RH. Range: -40 to 80°C. Slower but more accurate than DHT11.

💡 Example: Monitoring room temperature and humidity for HVAC control.

DS18B20

Waterproof digital temperature sensor. Accuracy: ±0.5°C. Range: -55 to 125°C. Multiple sensors can share one GPIO pin!

💡 Example: Monitoring freezer temperature with waterproof probe.

E

Edge Computing

Processing data on the device itself rather than sending everything to the cloud. Reduces latency and bandwidth usage.

💡 Example: ESP32 averaging 100 temperature readings locally before sending one value to the cloud.

ESP32

A powerful, low-cost microcontroller with built-in WiFi and Bluetooth. Dual-core 240MHz processor, 34+ GPIO pins, 520KB RAM.

💡 Example: The main microcontroller used in most OceanRemote projects.

ESP8266

The original low-cost WiFi microcontroller. Single-core 80MHz processor, 11-17 GPIO pins, 80KB RAM. Cheaper than ESP32 but fewer features.

EEPROM (Electrically Erasable Programmable Read-Only Memory)

Non-volatile memory that retains data after power loss. Used for storing settings like WiFi credentials or calibration values.

💡 Example: Saving device configuration so it persists after restart.

F

Firmware

The software programmed into a microcontroller's flash memory. OceanRemote generates ready-to-use firmware for ESP32/ESP8266.

Flash Memory

Non-volatile storage for your program code and data. ESP32 typically has 4-16MB flash. Retains data when power is off.

Floating Pin

A GPIO pin not connected to a defined voltage (neither HIGH nor LOW). Floating pins can cause erratic readings and increased power consumption.

💡 Example: Always use pull-up or pull-down resistors on unused input pins!

G

Gateway

A device that connects IoT sensors to the internet. Translates between different protocols (e.g., Zigbee to WiFi).

GPIO (General Purpose Input/Output)

Pins on a microcontroller that can be configured as inputs (reading sensors) or outputs (controlling LEDs, relays). ESP32 has 34+ GPIO pins.

💡 Example: pinMode(4, OUTPUT); digitalWrite(4, HIGH);

GND (Ground)

The reference voltage (0V) for all circuits. All components must share a common ground connection.

H

HMI (Human-Machine Interface)

The user interface that allows humans to interact with machines. In IoT, this could be a dashboard, mobile app, or physical controls.

Honeypot

A security mechanism that detects attackers by exposing fake vulnerable endpoints. OceanRemote uses honeypots to identify and block malicious probes.

HTTP (Hypertext Transfer Protocol)

The foundation of web communication. IoT devices often use HTTP to send data to APIs or receive commands.

💡 Example: ESP32 sending sensor data via HTTP POST request.

Hysteresis

A buffer zone that prevents rapid toggling. Used in temperature control to prevent relays from switching too frequently.

💡 Example: Turn heater on at 20°C, off at 22°C (2°C hysteresis prevents constant switching).

I

I2C (Inter-Integrated Circuit)

A two-wire communication protocol (SDA + SCL) for connecting multiple devices (sensors, displays) using just 2 pins. Supports up to 127 devices.

💡 Example: Connecting BME280, OLED display, and RTC to ESP32 using only GPIO 21 (SDA) and 22 (SCL).

IDE (Integrated Development Environment)

Software used to write, compile, and upload code. Arduino IDE and PlatformIO are most common for ESP32 development.

IndexNow

A protocol that instantly notifies search engines when content changes. OceanRemote uses IndexNow to get your projects indexed faster.

IoT (Internet of Things)

The network of physical devices embedded with electronics, software, and sensors to connect and exchange data over the internet.

IP Address (Internet Protocol Address)

A unique identifier for a device on a network. ESP32 gets an IP address from your router via DHCP or can use a static IP.

J

JSON (JavaScript Object Notation)

A lightweight data format used to exchange information between devices and servers. Easy for humans to read and machines to parse.

💡 Example: {"temperature": 23.5, "humidity": 65, "device": "sensor1"}

Jumper Wire

Pre-crimped wires with connectors used for prototyping on breadboards. Male-to-male, male-to-female, and female-to-female versions.

K

Kernel

The core of an operating system. ESP32 runs FreeRTOS kernel, which manages tasks and resources.

kΩ (kilo-ohm)

A unit of electrical resistance equal to 1000 ohms. Common values: 4.7kΩ, 10kΩ pull-up resistors.

L

Latency

The delay between a request and response. In IoT, low latency means fast response times for controlling devices.

LoRa (Long Range)

A wireless protocol designed for long-distance, low-power communication (up to 15km). Ideal for agricultural or remote sensors.

Library

Reusable code that adds functionality. OceanRemote provides libraries for easy device management and sensor reading.

M

MAC Address (Media Access Control Address)

A unique hardware identifier for network devices. Used for device authentication and network security.

Microcontroller

A small computer on a single chip. ESP32 and ESP8266 are microcontrollers designed for IoT applications.

MQTT (Message Queuing Telemetry Transport)

A lightweight publish/subscribe messaging protocol ideal for IoT. Uses minimal bandwidth and power.

💡 Example: ESP32 publishes temperature readings to a "sensor/temp" topic; your phone subscribes to receive updates.

µA (microamp)

One-millionth of an amp. ESP32 in deep sleep draws 5-150µA – critical for battery-powered projects.

N

NodeMCU

A popular development board based on ESP8266. Includes USB-to-serial converter and voltage regulator.

NO (Normally Open)

A relay contact that is open (off) when the relay is not energized. Closes when activated. Used for most applications.

NC (Normally Closed)

A relay contact that is closed (on) when the relay is not energized. Opens when activated. Used for safety systems.

NTC Thermistor (Negative Temperature Coefficient)

A temperature sensor whose resistance decreases as temperature increases. Very cheap ($0.10-0.20), requires calibration.

O

OceanRemote

An IoT platform for ESP32/ESP8266 devices. Provides cloud dashboard, firmware generation, and device management – all with a free tier.

OneWire

A communication protocol that uses a single data line plus ground. Used by DS18B20 temperature sensors. Multiple devices can share the same pin.

OTA (Over-The-Air) Update

Updating device firmware wirelessly without physical access. Critical for deployed IoT devices.

Optocoupler

A component that electrically isolates two circuits using light. Used in relay modules to protect microcontrollers from high-voltage spikes.

P

Partition Scheme

How flash memory is divided between application code, OTA updates, SPIFFS, and other data. ESP32 allows different partition layouts.

PCB (Printed Circuit Board)

A board that mechanically supports and electrically connects electronic components.

PIR Sensor (Passive Infrared)

A motion sensor that detects changes in infrared radiation. Used for occupancy detection and security systems.

PlatformIO

A professional development environment for IoT. Alternative to Arduino IDE with better debugging and library management.

PROGMEM

A keyword that stores constant data in flash memory instead of RAM. Saves valuable RAM for program execution.

PSRAM (Pseudo Static RAM)

Additional RAM connected to ESP32, typically 4-8MB. Allows larger programs and more data buffering.

Pull-up / Pull-down Resistor

A resistor that ensures a pin has a defined voltage (HIGH or LOW) when not actively driven. Prevents floating pins.

💡 Example: 10kΩ pull-up resistor on GPIO 4 ensures HIGH when button is not pressed.

PWM (Pulse Width Modulation)

A technique for simulating analog output by rapidly turning a digital pin on and off. Used for dimming LEDs, controlling motor speed, and servo positioning.

💡 Example: analogWrite(ledPin, 127); sets LED to 50% brightness.

Q

QoS (Quality of Service)

In MQTT, QoS levels determine message delivery guarantees: 0 = at most once, 1 = at least once, 2 = exactly once.

Query String

Part of a URL that contains data parameters. Used in API calls to send information.

💡 Example: https://api.oceanremote.net/data?device=123&temp=23.5

R

RAM (Random Access Memory)

Temporary memory for running programs. ESP32 has 520KB RAM, ESP8266 has 80KB. Data is lost when power is removed.

Relay

An electrically operated switch that allows a low-voltage signal (ESP32) to control high-voltage devices (lights, fans, appliances).

REST API (Representational State Transfer)

An API that follows REST principles using HTTP methods (GET, POST, PUT, DELETE). OceanRemote provides a REST API for device control.

RTC (Real-Time Clock)

Keeps accurate time even when the main processor is asleep or power is off. ESP32 has a built-in RTC.

RSSI (Received Signal Strength Indicator)

Measures WiFi signal strength in dBm. Closer to 0 is better (e.g., -30 dBm is excellent, -80 dBm is poor).

S

Sensor

A device that detects physical phenomena (temperature, motion, light, etc.) and converts it to an electrical signal.

Serial Communication

Sending data one bit at a time over a communication channel. UART is the most common serial protocol for debugging.

Sitemap

An XML file that tells search engines about pages on your website. OceanRemote generates sitemaps for better SEO.

SPI (Serial Peripheral Interface)

A 4-wire communication protocol (MOSI, MISO, SCLK, CS) for high-speed data transfer. Used for SD cards, displays, and some sensors.

SPIFFS (SPI Flash File System)

A file system for ESP32 flash memory. Used to store web pages, certificates, or configuration files.

SSID (Service Set Identifier)

The name of a WiFi network. Your ESP32 needs the SSID and password to connect.

SSR (Solid State Relay)

A relay with no moving parts. Silent operation, faster switching, longer life, but more expensive than mechanical relays.

Steinhart-Hart Equation

A mathematical formula used to calculate temperature from NTC thermistor resistance. OceanRemote firmware includes built-in Steinhart-Hart support.

T

TLS (Transport Layer Security)

Encryption protocol that secures internet communications. OceanRemote uses TLS 1.3 for all device-to-cloud communication.

Token

A unique identifier used for device authentication. OceanRemote uses secure tokens (registration tokens expire in 24 hours, permanent tokens are MAC-bound).

TOTP (Time-based One-Time Password)

A 6-digit code that changes every 30 seconds, generated by authenticator apps. Used for two-factor authentication in OceanRemote.

U

UART (Universal Asynchronous Receiver-Transmitter)

Hardware for serial communication. ESP32 has 3 UART interfaces (RX/TX pins). Used for debugging (Serial Monitor) and connecting to GPS, Bluetooth modules, etc.

ULP (Ultra-Low Power) Co-processor

A low-power processor in ESP32 that can read sensors while the main CPU sleeps. Extends battery life significantly.

UUID (Universally Unique Identifier)

A 128-bit identifier used in Bluetooth to identify services and characteristics.

V

VCC (Voltage at the Common Collector)

The positive power supply voltage (e.g., 3.3V or 5V). Often labeled VCC, VDD, or V+.

Voltage Divider

Two resistors in series that reduce voltage. Used with NTC thermistors and analog sensors.

Voltage Regulator

A component that maintains a constant voltage. ESP32 boards have a 3.3V regulator to power the chip from 5V USB.

W

Watchdog Timer

A hardware timer that resets the ESP32 if software gets stuck. Prevents crashes from infinite loops.

💡 Example: Add delay() or yield() in long loops to reset the watchdog timer.

WebSocket

A protocol for real-time, two-way communication. Better than HTTP for live data streaming.

WiFi

Wireless networking protocol used by ESP32 and ESP8266. 2.4GHz only – 5GHz not supported.

Wireless (WiFi) AP (Access Point) Mode

ESP32 creates its own WiFi network. Used for configuration portals or when no router is available.

Wireless (WiFi) STA (Station) Mode

ESP32 connects to an existing WiFi network (your home router). Most common mode for IoT devices.

X

X.509 Certificate

A digital certificate used for TLS/SSL encryption. Used to verify device identity in secure IoT deployments.

XML (eXtensible Markup Language)

A markup language for structured data. Sitemaps use XML format.

Y

YAML (YAML Ain't Markup Language)

A human-readable data format often used for configuration files in PlatformIO and Home Assistant.

yield()

A function that allows other tasks (like WiFi) to run. Prevents watchdog timer resets in long loops.

💡 Example: while(condition) { yield(); }

Z

Zener Diode

A diode that allows current to flow backwards when voltage exceeds a certain value. Used for voltage regulation and protection.

Zigbee

A low-power, low-data-rate wireless protocol for home automation (lights, locks, sensors). Requires a gateway/hub.

Z-Wave

A proprietary home automation protocol. Similar to Zigbee but uses different frequency bands (800-900MHz).

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