Modular buildings and modular homes are sectional prefabricated buildings or houses that consist of multiple modules or sections which are manufactured in a remote facility and then delivered to their intended site of use. The modules are assembled into a single residential building using either a crane or trucks.

Modular buildings are considerably different from mobile homes. Off-frame modular dwellings differ from mobile homes largely in their absence of axles or a frame, meaning that they are typically transported to their site by means of flat-bed trucks; however, some modular dwellings are built on a steel frame (on-frame modular), which can be used for transportation to the site. Many modular homes are of multi-level design, and are often set in place using a crane.

Modular buildings are very affordable because of the factory construction of these buildings. They are a very cost effective compared to conventional construction

Source:wikipedia