According to Valve, “Now in Beta! With Remote Play Together, you can now invite Steam Friends to join your local co-op, local multiplayer, and shared/split screen games online. Up to four players, can instantly join in the fun. Only the host needs to own and install the game, while additional players connect through Steam Remote Play streaming technology.”
For those who are unfamiliar with Remote Play Together, basically what this new feature does is that it allows gamers to play local multiplayer games online. This means that games that require all players to be present in the same location will now be able to play together in the comfort of their own home.
The best part is that only the host is the one that needs to install the game while the other players connect to them and they will be able to start playing. Note that due to the fact that this is currently in beta, you might encounter some issues, but it does sound like a fun new feature worth checking out.