What is it?
Of course, you know that brakes are used to slow and stop your car. But there are different kinds of brakes:

Disc brakes.
These are generally on the front wheels of your car. Disc brakes work like a vise, closing around the outer side of the vehicles rotor.

Drum brakes.
Found on the rear wheels, brake shoes push against the inside surface of a rotating brake drum to slow the vehicle.

Newer cars are also usually equipped with computer-controlled Anti-lock Braking Systems (ABS) and/or other traction control devices. This safety feature is designed to prevent wheel lock-up and potential skidding.