Before the introduction of the euro, francs were also used in France, Belgium and Luxembourg, while Andorra and Monaco accepted the French franc as legal tender (Monegasque franc).
Inside the caliper is a brake pad, a small block of friction material backed with a metal plate. When you step on your brake pedal, pistons inside the caliper cause it to apply pressure to the brake pad which squeezes the rotor, causing the car to slow or stop.
A caliper is part of the disc brake system. When you press the brake pedal, the brake fluid flows from the master cylinder to the calipers. Brake fluid then applies pressure on the piston inside the caliper, pushing the brake pads against the rotors to slow/stop your car. A car can have either 2 or 4 calipers.