Munkeh111 on 16 March 2009
Basically, when you kill people, or achieve objectives, you get XP and this levels you up. As you level up you unlock new weapons and perks, which give you things like faster reloading, more health, more grenades. There are also challenges which can give you XP and unlock new skins for your guns, so if you get 150 headshots with the AK-47, you get a golden gun
