Its simple. It means we give rewards (R+) to make behaviors increase in frequency (dogs sit when they want something) & we take away rewards (P-) when dogs do things we don’t like. Don’t be fooled by the the negative sign in (P-). It doesn’t mean bad/yucky. Scientifically speaking a (-) means SUBTRACT as in take-away. And Punishment is not a dirty word. Scientifically speaking a Punishment is anything that makes behaviors go down in frequency.
For example: Imagine you know a child who swears A LOT! To change that behavior you give them $1 for every day they don’t swear. This would be a reward (R+). You could also take away $0.50 for every bad word you catch the child saying. This would be a good example of removing a reward (P-) in order to make an undesirable behavior (swearing) go down in frequency.