The engine in your car has many roles to fill. It has to do more than move. It also has to generate electricity, assist with power steering, cool off the passengers, and keep itself cool. The serpentine belt - sometimes referred to as the fan belt, alternator belt, or accessory drive belt - is used to spin, or "drive," several components attached to the engine. It drives the alternator that powers the electrical system and recharges the battery. It also drives the power steering pump, the air conditioning compressor, and the water pump. (The water pump circulates coolant through the cooling system). In the past, multiple drive belts were used to turn pulleys attached to these components. Today, most vehicles employ just a single belt - the serpentine belt - to do the job.