Basically, you sign up to become a member, you get so many points, to start off with. Then you use those points to ask questions worth up to your limit of points.
The higher the points, the more likely you are to get fast/responses to your questions.
It's actually a nice community where you can get your questions answered, and also learn from all the Q&A asked from the past.
Also you can develop your problem solving skills, and learn to help other people out, for which you get graded and points.
It's a great site to learn and share from.