Most cars carry a "revenue" load, although "non-revenue" cars exist for the railroad's own use, such as for maintenance-of-way purposes. Such uses can generally be divided into the carriage of passengers and of freight. "Revenue" cars are basically of two types: passenger cars, or coaches, and freight cars or wagons.
In standard gauge cars, seating is usually between three and five seats across the width of the car, with an aisle in between (resulting in 2+1, 2+2 or 3+2 seats) or at the side. Tables may be present between seats facing one another. Alternatively, seats facing the same direction may have access to a fold-down ledge on the back of the seat in front.
Passenger cars can take the electricity supply for heating and lighting equipment from two main sources - either directly from a head end power generator on the locomotive via bus cables; or by an axle powered generator which continuously charges batteries whenever the train is in motion.
Modern cars usually have either air-conditioning or windows that can be opened (sometimes, for safety, not so far that one can hang out), or sometimes both. Various types of onboard train toilet facilities may also be provided.
Other types of passenger car exist, especially for long journeys, such as the dining car, parlor car, disco car, and in rare cases theater and movie theater car. In some cases another type of car is temporarily converted to one of these for an event.
Observation cars were built for the rear of many famous trains to allow the passengers to view the scenery. These proved popular, leading to the development of dome cars multiple units of which could be placed mid-train, and featured a glass-enclosed upper level extending above the normal roof to provide passengers with a better view.
Sleeping cars outfitted with (generally) small bedrooms allow passengers to sleep through their night-time trips, while couchette cars provide more basic sleeping accommodation. Long-distance trains often require baggage cars for the passengers' luggage. In European practice it used to be common for day coaches to be formed of compartments seating 6 or 8 passengers, with access from a side corridor. In the UK, Corridor coaches fell into disfavor in the 1960s and 1970s partially because open coaches are considered more secure by women traveling alone.
A "trainset" (or "set") is a semi-permanently arranged formation of cars, rather than one created 'ad hoc' out of whatever cars are available. These are only broken up and reshuffled 'on shed' (in the maintenance depot). Trains are then built of one or more of these 'sets' coupled together as needed for the capacity of that train.
Often, but not always, passenger cars in a train are linked together with enclosed, flexible gangway connections that can be walked through by passengers and crew members. Some designs incorporate semi-permanent connections between cars and may have a full-width connection, making in essence one longer, flexible 'car'. In North America, passenger equipment also employ tightlock couplings to keep a train reasonably intact in the event of a derailment or other accident.
Many multiple unit trains consist of cars which are semi-permanently coupled into sets; these sets may be joined together to form larger trains, but generally passengers can only move around between cars within a set. This "closed" nature allows the separate sets to be easily split to go separate ways. Some multiple-unit trainsets are designed so that corridor connections can be easily opened between coupled sets; this generally requires driving cabs either set off to the side or (as in the Dutch Koploper) above the passenger compartment. These cabs or driving trailers are also useful for quickly reversing the train.
Freight cars or (UK: "wagons" or "trucks") exist in a wide variety of types, adapted to the ideal carriage of a whole host of different things. Originally there were very few types of cars; the boxcar (UK: "van"), a closed box with side doors, was among the first.
Common types of freight cars include:
The vast majority of freight cars fit into the above categories.
Military armoured trains use several types of specialized cars: