Definition:
Disc brakes on a bicycle are brakes that slow the bike by acting on a disc mounted on the hub of the wheel. This is different from standard brakes, which press against the rim of the wheel.
With disc brakes, a rotor disc is mounted on the hub or axle and it spins inside a set of callipers attached to the frame or fork. Brake pads mounted on the callipers squeeze together on the disc to slow the wheel's rotation when the brake is engaged.
