Think of it as a low latency vnc server suitable for playing games on remote computers. If you want to play your PC games remotely on a raspberry connected to a tv, or on your iPad or laptop, this is for you. Basically self-hosted stadia. But I often use it for non gaming stuff instead of vnc because the latency is very low.

Nvidia gamestream is the proprietary server from nvidia, sunshine is an opensource server compatible with gamestream protocol, and moonlight is an opensource gamestream client.