The railway, also called railway line, ferro structure or railway, is the part of the railway infrastructure that connects two specific points in the territory and is made up of the following elements: track platform, superstructure, such as rails and counterrails, sleepers and fastening material, civil works such as bridges, viaducts and tunnels, and electrification, signaling and safety and telecommunications facilities on the track, service, and the elements that allow lighting.[1]​.

To build a railway, it is necessary to carry out earthworks and complementary works (bridges, drainage works, retaining walls, drains, etc.).

The elements of the railway lines[2]​ are grouped into.

Stations and terminals or other buildings or facilities serving travelers are not considered included in the concept of line.

The Track Circuit is part of the safety systems in the circulation of trains.

The turnouts "Detour (Railway)"), the switches "Point (Railway)") and the crossings "Crossing (Railway)") are part of the track devices.

The distance between the lanes is called gauge or track width, which coincides with the separation between wheels of the rolling stock. It is measured between internal faces, taking as a reference point the one located between 10 mm and 15 mm below the upper face of the rail, the difference depending on the type of rail and the standards applicable in the country.

The track works like a beam on an elastic bed") due to its own weight and the way the ballast behaves, an element intended for support and distribution of loads on the ground, and for containment. Since the beginning of railways, rails of reduced lengths were used, with expansion joints between them, which produced the characteristic rattling of railways, with treated wooden sleepers to prevent rot.

Currently, sleepers or sleepers made of prestressed concrete and plastic materials are mainly used on which welded rails with relatively long lengths and expansion joints that are further apart thanks to a more perfected design are supported.

Some historical dates of the railway related to the evolution of the track are the introduction of wooden rails in 1676, the iron lining of the rail in 1776, the cast iron rails in 1789, the railway detours in 1796, the Vignole type rail in 1836, the creosote of the wooden sleepers in 1838, the steel rails in 1857, the layout secant of the needles in 1886, the bi-block concrete sleepers in 1954, the single radius on diverted track in 1965, the monoblock prestressed concrete sleeper in 1979, the change with a speed of 100 km/h on a diverted track in 1986, the mobile tip heart for crossing the detours in 1992 and the change with a speed of 230 km/h on a diverted road in 1998.