As you move forward in the game, you can get achievements. You can complete these by answering a certain number of questions, suggesting, rating, and translating questions, amongst other things.
You can see your achievements by going into Profile and selecting Performance. There, you will see not only the achievements you have accomplished, but also the ones you have yet to accomplish. By selecting an achievement, you will be able to see the goal that has to be met in order to accomplish it and how close you are to getting it.
You can also see other players’ achievements by accessing their profiles and looking at their performance.