Are you feeling a frequent pulsating vibration as you press your brakes? It is highly likely that you are experiencing this because your brake rotors are unevenly worn. This happens when rotors get old and develop small cracks. As you use your disc brakes they will heat up, and that heat will not dissipate in a uniform manner throughout the rotor. Instead, it will create waves on the surface that you feel in the brake pedal and the steering wheel when you attempt to stop or slow down. Additionally, imperfections in the composition of the brake pads could wear grooves into the surface of the rotor causing a loss in functionality. Over time, disc brake rotors are just going to wear down and will eventually need to be replaced. Sometimes, the sides of the rotor can be skinned and shaved down slightly to make a more uniform and consistent surface. But if that's not possible (check with a brake technician), then replacing the brake rotors is your best option. And you don't want to play fast and loose with the very parts that are responsible for stopping and slowing down your car.
Disc brake rotors were first used on race cars for their superior responsiveness and stopping capabilities over drums. Seeing as the competitive racing space was, and still is, the proving ground for new innovations and technology, disc brake systems were continuously worked through and improved upon until automakers found them cost effective enough to offer on production vehicles. Essentially, a brake rotor is a flat disc that spins along with your wheel (attached at the wheel hub) and provides a double-sided surface upon which a caliper applies friction by pinching it with brake pads. This system was much more efficient and effective than the drum style brakes that came before it since brake rotors cool faster than drums, are more reliable in wet weather, and apply an even amount of force to the rotor surface rather than a shoe that applies more force in front of the drum than the rear.
Replacing you brake rotors is not very difficult at all. It can be done in about an hour using the appropriate torques and tolerances, and should always be done in pairs - meaning replace either both fronts or both rears at the same time.