The term commutation comes from the world of DC motors. It refers to how current is routed to the right coils, in the DC rotor, at the right time to generate the torque needed by using brushes and a commutator. A commutator is round, mounted on the rotor shaft and has conductive pads on the O.D. on which the brushes rest. Current is conducted from the brushes to the commutator and then to the connected coils as the rotor spins. This term has been carried over to brushless DC motors where the brushes and commutator have been replaced by electronics and a sensor on the rotor shaft. In this case current is still “switched” but by electronics. The term loses meaning in the world of AC motors but still sometimes refers incorrectly to how the AC voltage is generated in the drive.