An addiction is a chronic dysfunction of the brain system that involves reward, motivation and memory. It's about the way your body craves a substance or behavior, especially if it causes a compulsive or obsessive search for “reward” and a lack of concern for the consequences. Addiction is the inability to stop using a substance or engage in behavior even though it is causing psychological and physical harm. The disease model describes addiction as a set of chemical changes that occur in the brain.
While it remains a debated concept, it is the most widely used in treatment approaches.