The alternator is responsible for the electrical charge that moves through your engine and other electrical systems. Alternators are attached to the engine and move current through the engine, allowing your engine to continue running. As electric systems have advanced for cars in recent years, the alternator plays a bigger role in your car's electric efficiency.
Without an alternator or with a failing alternator, you likely will see a check engine light on your dash. This means that your car engine may suddenly shut off as it will not be able to hold a charge.