Puppy and dog play, just like all social predatory animals consists of practice predatory behavior and practice fight behavior.
More relaxed body and face postures, as well as the relative restraint during bites, mark the difference between the play and the mature forms of aggression.
Play aggression is used to teach young working dogs techniques before transferring over to more realistic training.
Play aggression can also cause a nuisance and even injury to pet owners and children if not channeled and managed properly. Nonetheless, it is handled differently and should not be confused with any of the mature forms.