What is a starter motor

This is a starter motor, it works hard.

Respect the starter motor, you rely on it every time to turn
your ignition key.

On top sits the starter motor solenoid, and when you connect it to a battery it pulls the 'actuating arm' in which in turn pushes the pinion shaft (that thing with the teeth on it, bottom left).

The pinion engages it's teeth with the teeth on the engines flywheel and the engine then turns (or cranks).

Starter motors can be located in very difficult positions, and it is advisable
to get a 'workshop manual' for your car so that it show's you the easiest
way to change yours.

Here is a starter motor and solenoid mounted on the engine.
Inside the gearbox casing (silver metal, top right) will be the flywheel that the
starter motor pinion will rotate to crank the engine.

A couple of photos showing the flywheel

This is only a brief explanation of the starter motor and starter motor solenoid.

If you want more detailed information on how to change them or how they
work, then click on one of the other articles shown below.