Track gauge refers to the distance between the inner edges of the two rails that make up a railway track. It is a critical measurement in railway design, as it affects the stability and speed of trains. Different countries and rail systems may use various gauges, with the standard gauge being 1,435 mm (4 ft 8 1⁄2 in). There are several types of track gauges, including narrow gauge, standard gauge, and broad gauge. Each type serves specific purposes, such as accommodating different types of trains or navigating challenging terrains. The choice of gauge can influence the interoperability of rail systems across regions.