short for popular culture. is pretty much anything that can be identified by the majority of the youth population. and when i say youth, i mean anyone from 6-30. in short, pop culture is jokes, practices, groups of people, and terms that are used by/funny to the majority of the youth population.
pop culture is referenced in movies a lot, especially in animated (or non-animated) adventure movies that can be watched and (mostly) understood by anyone. like putting internet memes or cat videos in a movie.