passenger train, freight train, electric trains, monorail, steam train, stealth train, Flyover
A train (English: train) is a form of rail transportation consisting of a series of vehicles pulled along a railroad track to transport cargo or passengers. The driving force is provided by separate locomotives or individual motors in units. Although historically steam engine propulsion predominated, the most common modern forms are diesel and electric locomotives, which are provided by overhead cables or auxiliary rails. Other sources of energy include horses, rope or wire, gravity, pneumatics, batteries and gas turbines. Railroads usually consist of two, three or four rails, with a number of monorails and maglev guideways in the mix. The etymology of the word "train" comes from the Old French trahiner, from the Latin trahere 'to pull, to pull'.[1]

There are different types of trains designed for specific purposes. A train may consist of a combination of one or more locomotives and attached railcars, or several self-propelled units (or sometimes a single or articulated powered coach, called a car train). The first chariots of this form were pulled using ropes, gravity powered or pulled by horses. From the early 19th century almost everything was powered by steam locomotives. From the 1910s onwards steam locomotives began to be replaced by less and cleaner (but more complex and expensive) diesel locomotives and electric locomotives, while at the same time multiple unit self-propelled vehicles as well as power systems became far more common in passenger service.