If I'm not mistaken, it runs straight off the browser, so no need to download anything. You can easily browse through games (or "experiences", as they're called) and join in.
It's very social because every game is multiplayer by default. If you ever played or heard of Second Life or VR Chat, it's not too different from them.
I suppose some of its games could damn well be run offline and locally, but that'd be bad for profits.