A railcar is a vehicle that runs on railroad tracks as part of a train. While most people think of trains as a single machine, they're actually made up of separate cars connected together: a locomotive (the engine that pulls everything) and railcars that carry cargo or passengers.

There are many types of railcars designed for different jobs. Boxcars are enclosed cars for shipping products like grain, electronics, or furniture. Tank cars carry liquids like milk, oil, or chemicals. Flatcars haul heavy items like lumber, steel beams, or even other vehicles. Hopper cars transport coal, gravel, or grain through openings at the bottom. And passenger railcars carry people, with seats, windows, and sometimes dining or sleeping areas.

A single freight train might include fifty or more railcars, stretching over a mile long. Each railcar can weigh over 100 tons when fully loaded. The word can also refer to a single self-propelled vehicle that runs on tracks, like a streetcar or trolley, though these usually operate alone rather than in long trains.