Used in place of something that was going to be said but would have been found inappropriate under the circumstances. Often in place of something that cannot be said on television, though being understood what would have otherwise followed.
Dude, I sent that guy a picture of my... Hey! Ewww man. That's just wrong.
A contraction for "Hello, I find you attractive and would like to dance with you, share some drinks with you, and then perhaps have sex with you. Nothing serious, of course, and I doubt that this will result in a long term relationship, but I would appeciate you considering my proposal."
Guy at bar to attractive girl: "Hey."
Attractive girl to guy: "Go to hell, creep." (Moves to other side of bar.)