MQTT is a lightweight publish/subscribe messaging protocol that is well-suited for IoT and mobile applications due to its low memory and network bandwidth requirements. Hobbyists and developers have used MQTT in a variety of fun and creative projects, such as getting rubber ducks to flash in sync with a phone, remotely watering a garden over the internet, and controlling a LEGO microscope. The protocol enables easy integration of devices like Arduinos and supports a wide range of programming languages and platforms.