A starter is an electrical motor that is connected to the battery. The job оf 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 оf starter is done. If the starter goes bad, the engine will not crank properly when you turn the ignition key in or may not crank at all.
The symptoms оf a faulty starter are like that оf a dead battery. Without the power from the battery, the starter cannot get the engine in motion. To determine if the problem is the battery or starter