Train

Train can mean either:

Space Train

Prohibited by all kinds of regulations, but still used by some cargo haulers because its cheaper than getting a real freighter. Basically, a tug is chained to the front of a cargo container with quick release cables, and burns all its fuel in the course of an hour or so to get up to high speed. At the half-way point, the tug detatches and allows the cargo to overtake, before recoupling at the rear end ready for a protracted period of deceleration.

City Train

Any type of ground vehicle (or rarely, in scattered worlds, a spacecraft) which runs along rails or cables. These are often simple to maintain, and can usually be automated to the extent that they only require a single button-press to start or stop. In many cases, they are the simplest and cheapest form of public transportation. Many trains are powered by current supplied through their rails from the power grid of the building or city they serve, or are winched along a cable by stationary engines at one end (or both). The carriage itself may be as simple as a metal box large enough to hold 2-6 people. Many buildings in cities have their own vertical trains, to allow easy ascent between levels.

If the cable or rail is a length of downline, then the train will often be referred to as an elevator. Otherwise, the colloquialisms lift, dropbox and boxcar are in common use in various parts of the universe.