I'm gonna hit the gym this summer and a friend of mine who's been lifting for over a year told me he's thinking of buying a pack of creatine pills, asking me if I want to contribute(the pack has 400 pills so it's quite expensive). I don't know much about it so please tell me more about it. What it is, is it worth it, what does it do, indications, etc.

EDIT: also, does it have anything to do with acne? Does it make it worse or something?

P.S: Originally posted this on the main sub but it seems I'm not experienced enough to make posts there. just in case.