What are rotors?

The primary definition of "rotor" is the metal circular disc... usually about 2/3 of an inch and varying in circumferance and removal mechanisms that attaches to the front axle spindle or the front axle out hub by your "studs" (lugs tighted the rotor onto the studs spindle, hub generally). The brakes pads are compressed by the "caliper" the caliper is governed by the brake pedel. YOU press very hard on the brake pedal... the caliper will compress TWO brake pads - on either side of the ROTOR grabbing it with friction and forcing the front axle to stop rotating as pressure is continually asserted upon the "rotor" by the "pads" through the "caliper" by the brake "pedal" applied by you. It is important to keep rotors - clean- straight (non-warped from too much tightening) turned- at each brake chage - have the rotors, as I said "turned" meaning "ground down to a slippery metal surface to optimize the pad application surface upon the rotor and a good contact between the two at EACH application of your foot upon the brake pedel. Lastly.... when buying... pads are a quick fix - rotors are not- sometimes you have to repack bearings and literally fight to get the rotor off... so buy a better grade rotor ... there are at least four (quality) tiers avalable... I see bembro listed quite often in these posts- they are special because they are drilled or slotted to create a cooler environment down there. After heavy stop and go traffic on interstates at night- watch the center area of the front wheels- and you may see a sports car's rotor glowing RED from heat. Anyway... hope this helps. 2dynamic

a brake rotor is the metal surface the brake pad is compressed against to slow down the vehicle. it spins with the wheels.

Answer Depends on what system you are talking about. A brake rotor is part of a disc brake system, and is the large, round, metal thing that your brake pads "squeeze" when applied. The pad contact with the rotor converts engergy of motion to heat energy, and that's what slows your car down. If the ignition system, the rotor is the rotating electrical contact in the distributor that channels voltage from the ignition coil to the individual cylinders.

In electrical engineering terms: in electric motors, dynamos/generators and alternators there are two different pieces used to create the electromagnetic field the units needs to work. the movable one is called the rotor and the fixed part is called the stator.