An ADU is a permitted second home with a complete kitchen, built on a single family home site. There are specific regulations that control the size and sometimes the use of an ADU.
An outbuilding is a structure built on a single family home site that is detached from the primary structure. It cannot have a complete kitchen. (It cannot contain any cooking appliances other than a microwave oven). Outbuildings have specific regulations and restrictions that differ from community to community.
Read more