Mobile homes or static caravans (in other countries; also called caravans) are prefabricated

Prefabrication

Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located...

 homes built in factories, rather than on site, and then taken to the place where they will be occupied. Being built on a permanently attached chassis with highway-grade wheels and tires, they are usually transported by being pulled behind a tractor-trailer over public roads to a home site.