An alternator is a type of electrical generator that converts mechanical energy into alternating current (AC) electrical energy. It is a common type of generator used in automobiles and other vehicles to provide power for the lights, accessories, and ignition system.

The alternator consists of a rotating magnet called the rotor, which spins inside a stationary set of coiled wires called the stator. As the rotor spins, it produces an AC current in the stator coils. This current is then fed to the vehicle's battery, where it is converted into DC power to operate the lights, accessories, and ignition system.

Most alternators are belt-driven, meaning they are connected to the engine's crankshaft via a pulley system. When the engine is running, the alternator is spun by the belts, which in turn generates electricity. Some alternators are also electrically powered, meaning they generate electricity through a set of brushes and commutators that rotate inside a set of stationary magnets.