Game Bans

There are several types of game ban in CS:GO :

VAC

Mostly happens when you used a detected cheat. These kind of bans are permanent, and you lose your inventory and cannot play matchmaking. HvH servers are fine though, because they always have VAC deactivated.

Overwatch Ban

Overwatch bans are manual bans where players watch your demos and ban you.

Griefing ban

Griefing bans are overwatch bans that are "minor", will last 30 days the first time, but will turn permanent if you get it twice.

Untrusted

Untrusted bans are similar to a VAC ban; permanent and skins are locked. Most cheats don't have untrusted bans. These bans can be caused due to features used in for example AimStep(Arms Race, Deathmatch and such) but every good cheat prevents the use of those features.