My original answer was:
A registered user usually gets 40 points for each answer accepted (but not necessarily correct). The points accumulate and this determines what level the user has reached. Users are promoted to the next level as the points pass a boundary determined by the people that control the site. There is no money or other material reward for the points. Points can be adjusted by people promoted to Administrator, who are also granted other privileges not available to other users. Points enable users' performance and activity to be compared, but the longer you have been a registered and active user, the more likely it is that you will accumulate points. If you click on Users in the menu bar, you can see a list of "top users", who have gained sufficient points to be listed. You can also pick a user and see their profile, recent activity, their questions and answers, etc. Remember that points don't always mean that users have answered questions correctly, and there are a lot of wrong answers as well as a lot of right answers! If you see a lot of answers to a particular question, you may be able to work out which answers are correct by examining and comparing answers. If everyone that uses the site asks and answers questions honestly, concisely and clearly, the site will be beneficial to everyone.