EMF= electromotive force  MMF= magnetomotive force RMF= rotating magentic field

The term emf is used for voltage generated by a source e.g. generator, battery or a photo cell. The term mmf is used in case of magnetic circuits. The term mmf in magnetic circuits is analogous to emf in electric circuits.EMF is generate in electric circuit which has conductors in the form ofcoil . A rotating magnetic field is a magnetic field that has moving polarities in which its opposite poles rotate about a central point or axis

if we see the long form of these terms u will get a little idea about it EMF - electromotive force <potential diff formed due to electric current> MMF - magneto motive force <pd formed due to in traction  of magnetic fields> RMF - rotating magnetic field

The term emf is used for voltage generated by a source e.g. generator, battery or a photo cell. The term mmf is used in case of magnetic circuits. The term mmf in magnetic circuits is analogous to emf in electric circuits. EMF is generate in electric circuit which has conductors in the form of coil .