Positive reinforcement is a behavioral concept where a desirable stimulus is presented following a behavior, increasing the likelihood that the behavior will be repeated in the future. This process involves providing a reward or incentive, which enhances the behavior and can lead to more consistent engagement in that behavior. In the context of reward systems and addiction, positive reinforcement plays a crucial role as it can encourage behaviors that are pleasurable, often leading to repeated actions such as drug use or other addictive behaviors.