A popular kid is a kid who lots of other people hang around; usually because of either what's in their parents pockets or what clothes they wear. The "un-popular" kids still talk to each other a lot, don't get me wrong, but "popular kids" usually are more exclusive in who they talk to. The term is a total joke, since popular kids are not really people that most people even like much. They just play along with them because they want to be noticed by them and not get bullied themselves.
Skit between a "popular kid" and a more popular student that is not so exclusive. (Brandan is trying to impress a girl)
Brandan: It is kinda funny how Derrick only has 49 friends on facebook.
Gina: He is trying to make friends, and already has some.
(Guy trips Derrick)
Brandan: (laughs) No, sorry, you are hot af but I don't think you are correct. Oh yeah, and Jasmine is a slut. (Brandan also laughs) Honestly, though, nobody could possibly have any affections for a guy like Derrick. Oh wow, look at Jason, he also sucks, Is he seriously wearing khaki pants that look like they are spilled; and a torn jacket; he is so poor (Gina still ignores)