A brake disc is usually an iron (or carbon composite) disc that is attached to the suspension of a car, motorcycle or even bicycle and is gripped by brake pads held in a brake caliper.
The friction between the brake disc and the pads is what brings the car to a halt.
The brake disc has numerous advantages over the brake drum, because it dissipates heat quickly, giving strong and consistent braking performance.
Disc brakes also give the driver more ‘feel’ at the pedal, allowing him or her to more easily modulate the pressure for a smooth stop.
In higher-performance applications, a brake disc will actually comprise two discs attached side by side by various rotors.
This, in effect, makes the disc ‘ventilated’ further helping cooling and performance.