The earliest evidence of a railway found thus far was the 6 kilometers Diolkos wagonway, which transported boats across the Corinth isthmus in Greece during the 6th century BC. Trucks pushed by slaves ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route. The Diolkos ran for over 1300 years, until 900 AD. The first horse-drawn wagonways also appeared in ancient Greece, with others to be found on Malta and various parts of the Roman Empire, using cut-stone tracks.

Railways began reappearing in Europe after a hiatus following the collapse of the Roman Empire from around 1550, usually operating with wooden tracks. The first railways in Great Britain (also known as wagonways) were constructed in the early 17th century, mainly for transporting coal from mines to canal wharfs where it could be transferred to a boat for onward shipment. The earliest recorded examples are the Wollaton Wagonway in Nottinghamshire and the Bourtreehill – Broomlands Wagonway in Irvine, Ayrshire. Other examples can be found in Broseley in Shropshire, where wooden rails and flanged wheels were utilised, as on a modern railway. However, the rails were prone to wear out under the pressure, and had to be replaced regularly…

There are various types of train designed for particular purposes. A train can consist of a combination of one or more locomotives and attached railroad cars, or a self-propelled multiple unit (or occasionally a single powered coach, called a railcar). Trains can also be hauled by horses, pulled by a cable, or run downhill by gravity.
Special kinds of trains running on corresponding special ‘railways’ are atmospheric railways, monorails, high-speed railways, maglev, rubber-tired underground, funicular and cog railways.
A passenger train may consist of one or several locomotives, and one or more coaches. Alternatively, a train may consist entirely of passenger carrying coaches, some or all of which are powered as a “multiple unit”. In many parts of the world, particularly Japan and Europe, high-speed rail is utilized extensively for passenger travel.
Freight trains comprise wagons or trucks rather than carriages, though some parcel and mail trains (especially Travelling Post Offices) are outwardly more like passenger trains.

Trains can also be ‘mixed’, comprising both passenger accommodation and freight vehicles. Such mixed trains are most likely to occur where services are infrequent, and running separate passenger and freight trains is not cost-effective, though the differing needs of passengers and freight usually means this is avoided where possible.

Special trains are also used for track maintenance; in some places, this is called maintenance of way.

In the United Kingdom, a train hauled by two locomotives is said to be “double-headed”, and in Canada and the United States it is quite common for a long freight train to be headed by three or more locomotives. A train with a locomotive attached at each end is described as ‘top and tailed’, this practice typically being used when there are no reversing facilities available. Where a second locomotive is attached temporarily to assist a train up steep banks or grades (or down them by providing braking power) it is referred to as ‘banking’ in the UK, or ‘helper service’ in North America. Recently, many loaded trains in the US have been made up with one or more locomotives in the middle or at the rear of the train, operated remotely from the lead cab. This is referred to as “DP” or “Distributed Power.”

The first trains were rope-hauled, gravity powered or pulled by horses. From the early 19th century almost all were powered by steam locomotives. From the 1910s onwards the steam locomotives began to be replaced by less labour intensive and cleaner (but more complex and expensive) diesel locomotives and electric locomotives, while at about the same time self-propelled multiple unit vehicles of either power system became much more common in passenger service. In most countries dieselisation of locomotives in day-to-day use was completed by the 1970s. A few countries, most notably the People’s Republic of China, where coal and labour are cheap, still use a few steam locomotives, but most have been phased out. Historic steam trains still run in many other countries, for the leisure and enthusiast market.

Electric traction offers a lower cost per mile of train operation but at a higher initial cost, which can only be justified on high traffic lines. Since the cost per mile of construction is much higher, electric traction is less viable for long-distance lines with the exception of long-distance high speed lines. Electric trains receive their current via overhead lines or through a third rail electric system.

A recent variation of the electric locomotive is the fuel cell locomotive. Fuel cell locomotives combine the advantage of not needing an electrical system in place, with the advantage of emissionless operation. However, the initial cost of such fuel cell vehicles is still substantial at the moment.

source