A train is a series of connected vehicles that run along a railway track to transport people or freight. These vehicles are typically pulled or pushed by locomotives, although some types, such as railcars or multiple units, are self-propelled. Passengers and cargo are carried within railroad cars, which are also commonly referred to as wagons or carriages.
Trains are designed to operate on a specific gauge, which is the distance between the rails. Most systems utilize steel wheels on steel tracks; this configuration provides low friction, making trains a highly efficient mode of transport. Rail transport is utilized by many countries worldwide.