Throughout the game you can earn achievements.
Clicking on the achievements button on the main interface (1) will take you to the achievements menu (2). The current achievement score will also be displayed on the button.
Achievements can be unlocked by completing their associated tasks (3). When completed they will award you with a certain number of achievement points (4).
Comparing achievements is another side of this feature.
By clicking on a friend’s portrait you can select “Compare Achievements” (1). This will take you to a side-by-side window (2), in which you can see your achievements paired with your friend’s.
You can also publish your achievements on social networks by pressing the “Share” button in the achievement interface (3) .