How does Active Directory work?
Active Directory is simply a hierarchical, object-oriented database that represents all of your network resources. At the top, there’s typically the Organization (O), beneath that Organizational Units (OU) as containers, and finally, objects that consist of your actual resources. This hierarchical format creates a very familiar and easy-to-administer tree for systems administrators. For example, if you assign an OU access to a given resource, that access will also be persisted to the objects that are contained within it.
