"Foreshadowing is when a character is covered by a parabola."
If rob = x
then y = pwn
Mike: "What the hell was that?"
Rob: "It's called foreshadowing hool who is filled with dick!"
Harry: What's a horcrux?
Snape: I'm no even going to tell you Harry, you'll find out soon enough.
You find out later, Snape knew there were horcruxes concerning Harry. This exemplifies foreshadowing.