On the Internet, you can be anything you want. Facebook thinks most people will want to be a generic floating body with a cartoon human head. They missed the point - self expression is what people want.
Do you mean "VRChat" maybe? I feel like Horizon will be more like an "Internet" where you can access other games/experiences. Not bare-bones, chat-only like VRChat, but that's just my guess.
Probably means Rec Room or Altspaces. With that said, VRChat is certainly not just bare bones chat. There are rooms for everything with all kind of games. Think Roblox.