An ADU is an Accessory Dwelling Unit. It is a separate unit on a property that has a single-family home, apartment, or other residential use. ADUs can go by many different names, including granny flats, in-law units, backyard cottages, secondary units, and more. The key difference between an ADU and other types of structures, such as pool cabanas, is they have living space, bedroom(s), and a kitchen. An ADU can be attached to the main home, the garage, or can be a standalone structure.
A JADU is a Junior Accessory Dwelling Unit. A JADU is different than an ADU in that they have to be part of an existing home and they have size restrictions. They can share the use of parts of the home, such as the bathrooms, and can have simpler kitchens with smaller appliances. JADUs are only allowed on a property with a single-family home on it, and the property owner has to live in either the single-family home or in the JADU. Development costs for a JADU are typically lower than an ADU.