You say something witty and charming, and that person laughs and smiles at you. This is an example of positive reinforcement.
Positive reinforcement is an important example of selection by consequences.
Well, at least the closest thing we've got. Research indicates that it is perhaps the most important tool for raising children, teaching students, managing performance in organizations, and solving social problems. Reinforcement depends on identifying a reinforcer that is effective with the individual, not always an easy task. Only behavior can be reinforced. Also, each person's reinforcers are different and sometimes idiosyncratic, and vary over time.