Electrical motor itself is well known for most of electrical engineers who have already studied in universities or so. However, it is not always well-known topics for researchers or engineers related to magnetic material or so. In order to research or design the magnetic material for an electrical motor or the related technologies, the magnetic researcher or engineer at least should know the fundamental concept of electrical motor. So the minimum contents of the summary from the fundamental theory of the electric motor, which are considered to be important for magnetic researcher, are extracted and are explained here. Fundamental theory of electrical motor is explained based on Maxwell equations. As a basic concept of electrical engineering, three-phase AC theory and traveling magnetic field are shown. AC motor theory and PM motor characteristics are finally explained, since they are mainly used in EV drive system.