A starter is an electrical motor that is connected to the battery. The job of a starter is to set the engine (pistons, crankshaft, etc.) in motion when you turn the ignition switch on. Once the engine starts and is in motion, the job of starter is done. If the starter goes bad, the engine will not crank properly when you turn the ignition key on or may not crank at all.
Symptoms of faulty starter
The symptoms of a faulty starter are similar to that of a dead battery. Without the power from the battery, the starter cannot get the engine in motion. In order to determine if the problem is the battery or starter, test the lights, radio, and horn. If they do not work, a dead battery is likely. If they work, it is more likely a problem with the starter. Since the starter is an electrical motor, it will eventually fail and require replacement during its service life.