Positive punishment involves presenting an aversive stimulusStimulus is defined as any change in the environment or... immediately following a behaviorBehavior refers to any activity or action that living o..., which decreases the likelihood of that behavior occurring in the future. In positive punishment, something is added to the environment to reduce an unwanted behavior.
Example
A child touches a hot stove and feels pain (aversive stimulus). The presentation of the painful sensation decreases the likelihood that the child will touch the stove again in the future. The addition of the unpleasant stimulus (pain) is the positive punishment.
Another example: If a student talks out of turn during class, the teacher may scold the student. The scolding (aversive stimulus) may decrease the chances that the student will talk out of turn again.