MQTT
In plain terms
A lightweight publish-subscribe protocol for IoT.
Going deeper
MQTT is a low-bandwidth, efficient messaging protocol designed for constrained devices and unreliable networks, common in IoT. It connects sensors cheaply.
Under the hood
Publish-subscribe via a broker with quality-of-service levels; minimal overhead suits battery/edge devices.
Examples
IoT sensors, home automation, telemetry, low-power devices, brokers.
Think of it like...
Like a tiny postal service optimized for sending brief messages over flaky connections.