Re: ???
It's just a 'team' wallpaper/backdrop.
So instead of individual's choosing their own backdrop for their stream (as available in Zoom), the recipient can select their own common backdrop for all streams in a call. Although it isn't clear whether each participant can set their own "Together" wallpaper or if it is imposed on all recipients on a call by the 'Teams' meeting convener.
Naturally, this begs the question as to where the video stream image manipulation processing is going on.
Given the video, I suspect it starts to fall apart if things get a little too dynamic, ie. people aren't behaving like 'perfect' talking heads.