Negative Reinforcement - This is most likely attention your pug will receive from you when he does something wrong. If he grabs your phone and starts to run around and you chase him yelling to get your phone back then he will learn that if he does that next time then he will be able to get that kind of attention from you.
Positive Reinforcement – Pugs love to make their owners smile. When they do something that grabs your attention and you praise and tell your pug what a good dog he is, he is learning that doing that good thing will give him the attention he wants. This is the kind of reinforcement you want your dog to get because it encourages good behavior.