What is the front part of a train that pulls the rest called?

A locomotive is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the use of these self-propelled vehicles is increasingly common for passenger trains, but rare for freight trains.

Traditionally, locomotives pulled trains from the front. However, push–pull operation has become common, where the train may have a locomotive (or locomotives) at the front, at the rear, or at each end. Most recently railroads have begun adopting DPU, or distributed power. The front may have one or two locomotives followed by a mid-train locomotive that is controlled remotely from the lead unit.