MQTT (Machine-to-Machine) is a machine-to-machine communication protocol that allows devices to publish messages to a broker under specific topics, and other devices can subscribe to those topics to receive information. It's popular due to its low bandwidth requirements, making it suitable for IoT devices with limited network connectivity. MQTT brokers connect to client devices, authenticate connections, and store data temporarily, enabling easy scalability as new devices are added to the architecture. Popular MQTT broker options include Mosquitto, EMQX, HiveMQ, AWS IoT Core, and Azure IoT Hub, each with their own pros and cons. Devices need to run client software to connect to a broker, with popular open-source options like MQTT X, Mosquitto's command-line interface, and HiveMQ's Java-based client library available. InfluxDB can integrate with MQTT by using plugins such as Telegraf input plugin or Native Collector, providing efficient data storage and analysis capabilities for IoT sensors collecting time series data.