Once Spotify is enabled via the Sonos app, users can stream to any Sonos speaker on the network, as well as create groups of speakers from within Spotify.
If you choose to play music to a Sonos group then all of the chosen speakers will playback simultaneously.
Somewhat dangerously you can also control the speakers remotely -- which is great if you want to scare the cat while you're at work.
Spotify Connect is the streaming service's proprietary connection protocol which enables users with compatible speakers to control their music and adjust volume over wi-fi. Sonos is the latest service to enable the system after Google Cast support was added last year. While Google Cast and Sonos speakers are able to be grouped among themselves unfortunately they aren't able to be grouped together.
Sonos announced the feature at a press conference in August 2016 and said it would be widely available with an update in early 2017. The company disclosed that the system would also be getting Amazon Alexa voice control at the same time.