An alternator is a machine in a car that makes electricity. It looks like a metal can with some wires sticking out of it.
Imagine you are playing with toy cars on a big track. You need batteries to make the cars move. But, batteries can run out of power quickly. An alternator is like a toy car battery that never runs out of power.
When you turn on your car, the alternator starts working. It takes energy from the engine and turns it into electricity. This electricity powers things like the lights, radio, and air conditioner in your car.
So, whenever you drive your car, you are also charging your car's battery with the help of the alternator. Without an alternator, your car would not be able to start or run smoothly.