This video has made the rounds before, but given that it is PMA season, we figured you might want to take a look at this video illustrating how camera lenses are made. There aren't any sex scenes (thank God) or explosions, but it is definitely cool and educational. Two words that are not normally used in the same sentence. [YouTube]
You mean, this shows how they make primes (fixed focal length), and you're interested in how they make zooms (variable focal lengths). A "normal" lens is one which provides a perspective about equal to the human eye; 50mm is considered normal in 35mm photography. A telephoto lens is one with a a focal length longer than the normal focal length, and a wide angle lens is one with a shorter focal length. For example, a 100mm lens is a telephoto, 70-300mm is a telephoto zoom, 24mm is wide angle, and 15-30mm is a wide angle zoom.