What are major types of trains?

The three major types of trains are steam, electric, and diesel.

Steam: The locomotive is powered by steam pressure. Traditionally, it is created by heating water using a coal-powered boiler. The boiler usually made up most of the locomotive.

Electric: The locomotive is powered directly from an electric source to power it's electric engine. Either from an overhead wire or third rail that are both charged with high voltage power.

Diesel: The locomotive is powered using diesel fuel to power the locomotive engine or prime mover. A common use of this fuel is diesel-electric. This is where the prime mover powers a generator that stores electric power that is then sent to electric motors known as "traction motors" mounted on each train axle that turn the wheels.