Motor vehicles and full-name power vehicles refer to the vehicles equipped with power devices in the rail transit system, including locomotives and power cars. Motorcycles are equipped with driving wheels, and the corresponding vehicle without driving device is a trailer. In order for a train to run normally on the track, it is necessary to have an EMU to provide sufficient traction for the whole train, but it can be trailer without power.

EMUs are railway vehicles equipped with wheel-driven machinery, not EMUs. There are not only EMUs in high-speed trains, but also EMUs in all types of trains, including constant-speed EMUs, ordinary-speed trains, Metro trains, light rail trains, monorail trains and maglev trains.