The part of a pop song which causes you to want to hear it again. Probably the best parody of this idea is by Blues Traveler in their song by the same name on their 1994 CD, Four. However, a good hook is always a thing of beauty. One modern band who has the concept of a hook down pat is Fastball. Their song, The Way, has one of the best hooks of the decade.
Alternately, a golf shot which travels from the right to left, for a right-handed player.