Active Directory

Active Directory (AD) is a database and set of services that connect users with the network resources they need to get their work done. The database (or directory) contains critical information about your environment, including what users and computers there are and who’s allowed to do what.
The Active Directory structure is comprised of three main components: domains, trees, and forests. Several objects, like users or devices that use the same AD database, can be grouped into a single domain.