Achievements are special unlockables exclusive to the Xbox 360. How to unlock achievements varies in every game. Sometimes they come in normal progression through the game; sometimes they can only be unlocked by collecting special items or finding a hidden one. When achievements are unlocked, a special amount of points is added to your gamerscore. This gamerscore shows overall how much skill in games you have, how many games you have and how many achievements you have unlocked. The more difficult the achievement, the more points given out.