A train is a connected series of vehicles that move along a track (permanent way) to transport freight or passengers from one place to another.
The track usually consists of two rails, but might also be a monorail or maglev guideway.
Propulsion for the train is provided by a separate locomotive, or from individual motors in self-propelled multiple units.
Most modern trains are powered by diesel locomotives or by electricity supplied by overhead wires or additional rails, although historically (from the early 19th century to the mid-20th century) the steam locomotive was the dominant form of locomotive power.
A toy train is a toy that represents a train. It is distinguished from a model train by an emphasis on low cost and durability, rather than scale modeling.
A toy train can be as simple as a pull toy that does not even run on track, or it might be operated by clockwork or a battery.
Many toy trains blur the line between the two categories, running on electric power and approaching accurate scale.
The earliest toy trains date from the 19th century and were often made of cast iron. Motorized units running on track soon followed, powered by a steam or clockwork engine. Some of these trains used clever methods to whistle and smoke.
Many modern electric toy trains contain sophisticated electronics that emit digitized sound effects and allow the operator to safely and easily run multiple remote control trains on one loop of track.
Consumer interest in trains as toys waned in the late 1950s, but has experienced resurgence since the late 1990s due in large part to the popularity of Thomas the Tank Engine.