Properly called caliper disc brakes, these are a type of brake with a kidney-shaped brake pad that consists of a rotor that rotates at wheel speed, straddled by a caliper that can squeeze the surfaces of the rotor with brake pads near its edge.
Disc brakes provide a more linear response and operate more efficiently at high temperatures and during wet weather than drum brakes.
Hydraulic brakes were a major technological change, because it ensured that an equal braking force was applied on each wheel.
The break-pedal is connected to a master-cylinder, filled with hydraulic oil. When the driver exerts pressure on the break-pedal, the oil is pumped through a tube (known as a circuit) which is routed to each of the four wheels.
The oil pumped through the circuits activates a piston, which exerts pressure on each wheel. Ventilated disc brakes add special vents inside the disc (that you can see along the edge of the disc). These vents help move cooling air through the disc for better braking performance and less brake fade.