A brake rotor (or disc) is a metal disc, mounted to the hub of each equipped wheel. When the brakes are applied, the brake pads are forced against the brake rotor and slows down and stops your vehicle. Most new vehicles have disc brakes on the front wheels and drum brakes on the rear wheels. Luxury cars tend to have disc brakes on all four wheels.
The most common problem with the brake rotor is that the brake pad material wears over time. If the brake pads are not replaced when needed, then the metal backing of the pads can become exposed. If the metal backing becomes exposed, then it can wear grooves into the brake rotor causing damage. Also, if the brake rotors are not tightened correctly when installed, then they can warp.
While most manufacturer's factory warranty and extended auto warranties do not cover the cost of replacing a brake rotor, there are maintenance plans available that will cover the cost of a brake pad inspection, which will allow the technician to determine if the brake pad needs to be replaced and will also cut down on the frequency of a brake rotor replacement.