: a building used for guests (as on an estate) especially : a house run as a boardinghouse or bed-and-breakfast.

A guesthouse is a small building, close to, but not attached to the main house on a property. it functions in the same way a guest bedroom does, and in some cases has has full kitchen and living areas.

A casita built from converted space is usually referring to a basement, attic, or garage conversion. The city of Scottsdale has rules around what can be classified as a casita/guest house. A guesthouse is an accessory building or portion of the main building used to house guests of the occupants of the main building.

In some areas of the world, guest houses are the only kind of accommodation available for visitors who have no local relatives with whom to stay. Among the features which distinguish a guest house from a hotel or inn is the lack of a full-time staff.