Alternators

An alternator is a main component of a vehicles charging system. It does this by converting alternating current (AC) into direct current (DC) which can be then received by the battery. An alternator is an electromagnet that is driven off of engine power through the pulleys.

The picture above shows an alternator in its full glory. The black thingy on the side, that would be the pulley and the driving force of the alternator.

To be quick, and simple about it to avoid mucking my thoughts up.  Electron current is induced when the Rotor spins inside the stator. The Rotor receives its current through a pair of slip rings attached to the rotor shaft. The current is passed on from the voltage regulator through a pair of brushes which come in and out of contact of the slip rings while they are rotating. The stator is a group of conductors that pass alternating current into the rectifier where it becomes a direct current which can be then absorbs by the batterey. The stator itself is a group of conductors that induce current as the rotor's electromagnetic field cuts across the conductors. As the electromagnetic field is both positive and negative current is produced in two differing directions which can not be sent to the battery(+) as is.

Above:  A typical alternator circuit.