Hot rolled steel in the profile (cross section) of an asymmetrical I-beam is usually used as the surface on which railway wheels run. Unlike some other uses of iron and steel, railway rails are subject to very high stresses and have to be made of very high quality steel alloy. It took many decades to improve the quality of the materials, including the change from iron to steel. The heavier the rails and the rest of the trackwork, the heavier and faster the trains the track can carry.

Profiles of rail include:
1- Bullhead rail
2- Grooved rail
3- Vignoles rail (flat-bottomed rail)
4- Flanged T rail
5- Bridge rail (inverted U)
6- Barlow rail (inverted V)

North American railroads until the mid- to late-20th century used rails 39 ft (11.89 m) long so they could be carried to and from a worksite in gondola cars (open wagons), often 40 ft (12 m) long; as gondola sizes increased, so did rail lengths. The world's longest rail sections are 120m long and are made by various companies.

Bullhead rail
Bullhead rail is similar to double-headed rail but with a heavier profile to the top edge. It became the standard for the British railway system until the mid-20th century but has now been largely replaced by flat-bottom rail. Bullhead rail is still used on the London Underground and survives on the national rail system in some sidings.
Grooved rail
A grooved rail, groove rail, or girder rail is a special rail designed for tramway or railway track in pavement or grassed surfaces (grassed track or track in a lawn).
Vignoles rail
Vignoles rail is the popular name of the flat-bottomed rail used internationally for railway track.
Flanged T rail
Crossties or sleepers constructed of concrete are in use in some places. The use of creosote as a treatment for wooden crossties has been declared to be detrimental to the health of people and plants. The use of creosote as a preservative treatment for wooden crossties has been approved in the U.S., and is widely used in other countries.[citation needed] The crossties or sleepers are embedded in ballast in order to provide stability and drainage.

The joint where two rails are connected is the weakest part of a rail line. The earliest iron rails were joined by a simple fishplate or bar of metal bolted through the web of the rail. Stronger methods of joining two rails together have been developed. When sufficient metal is put into the rail joint, the joint is almost as strong as the rest of the rail length. The noise generated by trains passing over the rail joints, described as "the clickity clack of the railroad track", can be eliminated by welding the rail sections together forming a continuous rail. One kind of welding is the Thermite welding process.

Baulk rail (Bridge rail)
Baulk road is the name given to a type of railway track or 'rail road' that is formed using rails carried on continuous timber bearings, as opposed to the more familiar 'cross-sleeper' track that uses closely spaced sleepers or ties to give intermittent support to taller rails. Baulk road was popularised by Isambard Kingdom Brunel for his 7 ft 0 1⁄4 in (2,140 mm) broad gauge railways in the United Kingdom, but has also been used for other railways and can still be found in modified form in special locations on present day railways.

A variant of baulk road can still be seen today on some older under-line bridges where no ballast is provided. The design varies considerably, but in many cases longitudinal timbers are supported directly on the cross-girders, with transoms and tiebars to retain the gauge, and modern rails and base-plates or chairs laid on top. It can also be found in places where easy drainage is required.

Barlow rail
Barlow rail was a rolled rail section used on early railways. It has wide flaring feet and was designed to be laid direct on the ballast, without requiring sleepers. It was widely adopted on lightly trafficked railways, but was ultimately unsuccessful because of maintenance difficulties.

  source: wikipedia.org,