(in the song crank dat by soulja boy, he often says you with a long o)
Ok, not really. But you know it still sounds cool.
In literal terms, it is a pronoun in second person. And if you don't know what that means....go to English class.
Person 2: Yooooooooooooooooooooou!
Person 1: You need to go to English class.
Person 2: Why?
Person 3: Because you had to look up the definition for you!