MQTT is a communication protocol for IoT devices. It is super cool, but setting it up can be confusing. It consists of a MQTT broker, a central node that all clients connect to and which is responsible for handling and passing on messages, and the the MQTT clients. Since Arduino comes with a MQTT you can build a MQTT client into all sorts of things.
If you use OpenHab you will have to set up the following „Things“:
- MQTT broker bridge: connects to broker
- MQTT thing: connects to bridge