Multiroom systems or multiroom audio systems are audio systems that allow for playback and control of music throughout an entire home or building.
This means that you are able to play (stream) the same music on several speakers and not only one. You can easily create groups of speakers and control them all at once.
There are many systems that provide this functionallity. Audio Pro is one of them. There are also e.g. Airplay 2 and Google Chromecast.