The battery and charging system provide the power to start the car and to run all the accessories and electronics. The primary job of the battery is to provide electrical power to run the starter motor, which spins the engine until it can run on its own. The battery is also a stabilizing influence in the electrical system when the engine is running. A weak or dead battery can easily cause a "no-start" condition and leave you stranded.
The alternator’s job is to produce electricity to recharge the battery and to provide for all the other electrical needs of the vehicle.
The only job of the starter is to spin the engine so it can start and run on its own, like pulling a rope on a lawn mower or outboard engine.
A malfunction in any of these components will leave you stranded if not addressed. Oddly enough, a battery light usually indicates an alternator problem, not a battery failure. Battery life in Florida is typically shorter than in cooler areas of the country, and batteries here frequently fail without warning. When your car would crank slowly during those first cold autumn days up north you were reminded that you had an old battery. Not so here - frequently folks go grocery shopping and come back to the car with ice cream, only to find they are stuck. That’s why we check batteries during oil changes in an effort to prevent that from happening to you!