Oh, sorry, I somewhat forgot that other people don't share the same knowledge of acronyms as me, sorry, little tired.

CS:GO stands for 'Counter-Strike: Global Offensive', a game published and released by Valve, you can find more info here (click me!). I'm selling a giftable copy (Activates on any Steam account, you can also trade it, as, it's an inventory copy), you can play on either Windows, or, Mac, and, hopefully soon Linux (Although, no ETA). It's the successor to Counter-Strike: Source, and, a relatively fun game.