Punishment is the opposite of reinforcement. Reinforcement is meant to increase a behavior while punishment is meant to decrease a behavior. There are two types of punishment such as positive punishment and negative punishment. Positive punishment is the administration of an aversive stimulus, for example spanking. Negative punishment is the withdrawl of a desireable stimulus, for example time-out from privileges. Even though punishment suppresses unwanted behavior, it often does not guide one toward more desirable behavior. Punishment combined with reinforcement is usually more effective than punishment alone. If the punishment is avoidable, the punished behavior may reappear in safe settings.


Sources:

Myers, D. G. (2007). Psychology (8th ed., pp. 332-333). New York: Worth Publishers.