An ADU, or additional dwelling unit, is a separate living space within a single-family home or on the same property as a single-family home. ADUs are also sometimes called "granny flats," "in-law units," or "secondary units." They can be used as a rental property, a place for aging family members to live, or as a home office or studio. ADUs can be located in a basement, above a garage, or in a separate structure on the property. They are often small, with their own kitchen, bathroom, and living space. ADUs are becoming increasingly popular as a way to provide more housing options in areas with high real estate prices and tight housing markets.