do you mean rotor as in helicopter, and propeller as in aeroplane?
a rotor is a much more general term and hence it is flexible about its definition, and it encompasses more functionalities... in a plane propeller , it is specific for 'propelling' the plane in one axis through the air, so the most you can do is alter the collective pitch of the blades ... in a helicopter rotor, it provides 3 axes of movement, the collective pitch provides one axis while cyclic pitch provides the other two
also, propellers tend to be called 'air screws' because if you look at a propeller-driven plane in flight but in slow motion, that is what the propellers appear to be doing
while 'rotor' can include the parts of some machine which functions by spinning, like an electric motor or an automotive brake