Bosch Starter

The Car Starter works by harnessing the power of the automotive battery. Once the key is inserted into the ignition switch and then turned to the start position, a tiny amount of current flow through the neutral safety switch and into the starter relay or Starter Solenoid. The Starter Motor then cranks the engine to enable the piston to create a suction drawing in the fuel and air mixture into the cylinder. The engine will then start as the spark created by the ignition system will ignite this mixture. 

Turning on the ignition switch allows a small amount of power from the battery to flow to the solenoid above the starter. When the low-current power from the starting battery is applied to the solenoid, oftentimes with a key-operated switch, it releases a small pinion gear on the starter motor's shaft and meshes it with the ring gear on the flywheel of the engine. 
The solenoid is also responsible for closing out high-current contacts for the starter motor and it then starts to run. Once the engine starts, a key-operated switch is activated and a spring in the solenoid assembly pulls the pinion gear away from the ring gear which then causes the starter motor to stop. Modern AUTO STARTER motors are equipped with a "bendix," a gear and integral freewheel, or overrunning clutch, thereby allowing the flywheel to automatically disengage the pinion gear from the flywheel when the engine starts.