The starter motor converts electrical energy to mechanical energy and is mounted on the cylinder block in a position to engage a ring gear on the engine flywheel.
Starting is usually accomplished by the operator activating a starter switch as part of ignition key operation. This allows a relatively small current to flow to a starter solenoid relay and operate a plunger attached to a drive pinion engagement lever.
The plunger movement engages the drive pinion with the ring gear and closes a set of heavy duty contacts, allowing a large current to flow from the battery to the starter motor, rotating the armature and drive pinion, and causing the crankshaft to spin.
When the engine starts and is able to run on its own, the operator usually releases the key and this withdraws the pinion from the ring gear and brings the armature to a halt.