A compulsion loop is a sequence of activities that makes you continue the sequence of activities. The loop rewards you for every completion with a bit of dopamine, keeping you hooked.
The point of most games (and gamified systems) is to keep you on this loop for as long as possible, before you realize what they are doing.
While this kind of loop is most easily noticeable in games, you can see a similar loop underlying nearly all compulsive behavior that isn't due to physical matters (like drugs or illnesses).
What loop are you on?