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.
On most cars, the next step is to remove the brake caliper so the brake pads will slide out through the top. On a few cars the pads will come out without removing the caliper, but not many. You'll see the brake caliper in the 12 o'clock position just above the lug bolts, riding atop that shiny brake disc.