A rotor is called that because it rotates. It is fastened to the distributor shaft. The distributor shaft is mechanically connected to the camshaft. The camshaft opens and closes valves that let in oxygen and fuel and let out, or exhausts, burned fuel and oxygen. It burns because the distributor distributes spark to the distributor cap, thru the rotor, which in turn sends that spark to the spark plugs. It must happen in exact sequence to run properly. Any problems along those parts results in that spark occurring at the wrong time, which causes all kinds of driveability problems.
The problem here is I try to relate too much info. I am a mechanic, not a teacher.