A trailer is generally an unpowered vehicle pulled

Towing

Towing is the process of pulling or drawing behind a chain, line, bar or some other form of couplings. Towing is most visibly performed by road vehicles, but anything from waterborne vessels to tractors to people can tow cargo. Troop carrying and cargo carrying gliders were towed behind powered...

 by a powered vehicle. Commonly, the term trailer refers to such vehicles used for transport of goods and materials.

Sometimes recreational vehicle

Recreational vehicle

Recreational vehicle or RV is, in North America, the usual term for a Motor vehicle or trailer equipped with living space and amenities found in a home.-Features:...

s, travel trailer

Travel trailer

A travel trailer or caravan is towed behind a road vehicle to provide a place to sleep which is more comfortable and protected than a tent . It provides the means for people to have their own home on a journey or a vacation, without relying on a motel or hotel, and enables them to stay in places...

s, or mobile home

Mobile home

Mobile homes or static caravans are prefabricated homes built in factories, rather than on site, and then taken to the place where they will be occupied...

s with limited living facilities, where people can camp or stay have been referred to as trailers. In earlier days, many such vehicles were towable

Towing

Towing is the process of pulling or drawing behind a chain, line, bar or some other form of couplings. Towing is most visibly performed by road vehicles, but anything from waterborne vessels to tractors to people can tow cargo. Troop carrying and cargo carrying gliders were towed behind powered...

 trailers.

United States

In the United States, the term is sometimes used interchangeably with travel trailer

Travel trailer

A travel trailer or caravan is towed behind a road vehicle to provide a place to sleep which is more comfortable and protected than a tent . It provides the means for people to have their own home on a journey or a vacation, without relying on a motel or hotel, and enables them to stay in places...

 and mobile home

Mobile home

Mobile homes or static caravans are prefabricated homes built in factories, rather than on site, and then taken to the place where they will be occupied...

, varieties of trailers and manufactured housing designed for human habitation. Their origins lay in utility trailers built in a similar fashion to horse-drawn wagons. A trailer park

Trailer park

A trailer park is a semi-permanent or permanent area for mobile homes or travel trailers. The main reasons for living in such trailer parks are the often lower cost compared to other housing, and the ability to move to a new area more quickly and easily, for example when changing jobs to another...

 is an area where mobile homes are placed for habitation.

In the United States trailers ranging in size from single-axle dollies

Dolly (trailer)

A dolly is a small trailer that can be coupled to a truck or trailer so as to support a semi-trailer. The dolly is equipped with a fifth wheel to which the semi-trailer is coupled...

 to 6-axle, 13 in 6 in (4,114.8 mm) high, 53 in 0 in (16,154.4 mm) long semi-trailer

Semi-trailer

A semi-trailer is a trailer without a front axle. A large proportion of its weight is supported by a road tractor, a detachable front axle assembly known as a dolly, or the tail of another trailer...

s are commonplace. The latter, when towed as part of a tractor-trailer or "18-wheeler", carries a large percentage of the freight that travels over land in North America.

Types of trailers

Some trailers are made for personal (or small business) use with practically any powered vehicle having an appropriate hitch

Tow hitch

A tow hitch is a device attached to the chassis of a vehicle for towing or a towbar to an aircraft nose gear, or paired main gears....

, but some trailers are part of large trucks called semi-trailer truck

Semi-trailer truck

A semi-trailer truck, also known as a semi, tractor-trailer, or articulated truck or articulated lorry, is an articulated vehicle consisting of a towing engine , and a semi-trailer A semi-trailer truck, also known as a semi, tractor-trailer, or (in the United Kingdom and Ireland) articulated truck...

s for transportation of cargo

Cargo

Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...

.