All Mountain Bike Parts Descriptions

#19) Brakes - The stoppers.
  There are several types of brakes available: Caliper, Cantiliver, U-brake, V-brake, Coaster, Drum, and now Disc brake sets. All of these designed to help you stop (or you can just drag your feet on the ground). Some brake styles work better than others, it all depends on what you need them for. All brakes use some sort of "shoe" (again, back to the old dragging your feet on the ground technology) Whether dragging on rims, drums or rotors, they all use specifically built "shoes"
  Brakes that work off the rims to slow down, use the least amount of force because they are stopping the wheel from the outer circumference. This centrifical force of a spinning wheel is easier to slow down out by the rim.
   The Disk and Drum brakes slow down the wheel from closer to the center of the wheel so more pressure at the brake lever is needed to do the same job. Rim brakes may have the advantage of being lighter, simple to mantain, and brake pads are cheaper, but the disc brakes have some big advantages too. They don't wear out the sidewalls of your rims like Rim brakes do, nor do they get in the way if you have to ride home on warped or dented wheels. Disc brakes mostly use a hydraulic fluid system which can provide enough power to the rotors to overcome the centrifugal force to stop. They also have a very consistant feel, which is very important if you ever want to learn how to do a nose-wheeley.

Bike Parts Diagram