Positive punishment is meant to while negative reinforcement is meant to

Positive punishment is meant to decrease (undesirable) behaviors while negative reinforcement is meant to increase (desirable) behaviors.
When it comes to a positive punishment, you just present a person with negative consequences that will arise from their behavior, and they will understand why that is unacceptable and stop doing it. Negative reinforcement is removing a negative stimulus from a situation so as to ensure that only positive events will occur.