Okay kiddo, when a car goes fast, it needs something to help it stop. That's where the brakes come in! Now, when you press on the brake pedal, it makes something called the brake pads squeeze down on the wheels. The brake pads are made of a strong material called brake lining that rubs against the wheels to stop them from spinning.
Imagine if you had a toy car and you wanted it to stop moving. You could press your hand down on the back wheels to slow it down, right? That's kind of what the brake pads do for a real car. But the wheels of a real car are much bigger, so the brake pads need to be stronger and last longer. That's why they use a special kind of material called brake lining.
But over time, the brake lining can wear down from all the rubbing against the wheels. When that happens, you need to take the car to a mechanic to get new brake pads with fresh brake lining put on. That way, the car can keep stopping safely whenever you need it to.