Garry's Mod

Could someone inform me what's going on with Garry's mod?

So there's a Gmod 13 BETA going right now
So i got 2 question's!
1) It's a patch or a new game?
2) What game do you need to get the 'basic" props for Garry's mod ( i think it's Half Life 2 , could be wrong )

You don't need anything for Garry's mod and there's no beta going on and Garry's mod is its own game.

There is a beta going on its like the biggest gmod news how can you not know about it and its going to be a update not its own game!.