game free (0 dollar)
but you can't play multiplayer or the inventory skin trading thingy or anything you gotta buy the full game (or as valve calls it, a license)
you can play with bots (beep boop)
also you can get maps from the workshop (i got a map thats just a field with a bunch of chickens i like pressing e for them to follow me)
also apparently you can spectate like esports or whatever i think