OU (organizational unit)

An Active Directory container object used within domains. An organizational unit is a logical container into which users, groups, computers, and other organizational units are placed. It can contain objects only from its parent domain. An organizational unit is the smallest scope to which a Group Policy object can be linked, or over which administrative authority can be delegated. An Active Directory container that can have one or more Group Policies applied. It can also hold other containers as well as Users, Computers, and Groups. Permissions can be assigned to OU's using Access Control Lists.