A subDAO is a DAO derived from another ('parent', 'super') DAO, analogous to a subsidiary company. A subDAO may or may not operate under the control of its parent DAO.
At origination, subDAOs are rationally economically aligned with their parent DAO. Generally, subDAOs are created to serve as specialized focus groups of DAO members or activities. However, provided sufficient incentives and mechanisms, subDAOs may elect to become more economically independent from super DAOs over time.