Auto Parts: Serpentine Belts, serpentine belts, serpentine belt

Question
What does a serpentine belt control? How does it work? What will happen if a serpentine belt breaks?

Answer
    A serpentine belt does the same job that v-belts used to do on older cars.  In other words, it's your fan belt, even though you may not have a belt-driven fan.  The reason that these flat, multi-grooved belts are used is twofold.  They last longer.  This is because they run cooler.  And, they are more efficient.  An old-fashioned v-belt uses a lot of energy when it is forced down into the groove of the pulley on the way in and ripped out of the groove on the way out.  As a bonus, with proper design, a serpentine belt can be made to drive on the smooth side and the grooved side.  By snaking (serpentine-get it?) it around all of the pulleys, all of the engine-driven accessories can be driven by just one belt.  Downside is that, when the belt breaks, everything quits working.  But, since the belt will last many times longer than the old-fashioned v-belt, routine maintenance should be enough to keep this from happening.