1) You know how birds fly in V-formation and the first bird is doing most of the work? The rest are drafting; they don't have to work as hard to keep up.
2) Clipless pedals .. if you have a shoe with a cleat in it that's designed to lock into the pedal, that's a clipless pedal. The story as I understand it: Track racers actually bolt their shoes onto their pedals, and those are called "clips." Clipless are clipless because you're not bolted on; you have a release mechanism. (Note though that most people call the plastic basket thingies toe clips instead.)