The term "negative reinforcement" is often confused with "positive punishment". Here's why.
The easiest way to remember the definitions is to think of "positive" as adding something (desirable or undesirable) and "negative" as taking something away (desirable or undesirable) .
Both forms of punishment reduce a behaviour but they do not guarantee that the unwanted behavior won't occur again. Because the behavior stops, at least temporarily, punishment is reinforcing to the punisher. Punishment creates unpredictable and unwanted side effects such as fear and aggression which makes it a training choice of last resort.