Many vendors build specialised repositories or directory services into their applications and devices to enable the specific functionality their customers require. For example, e-mail products include directory services that let users look up and send mail to others. Server operating systems use directory services for features such as user account management and storing configuration information about applications.

Because these directory services are targeted narrowly to the needs of the application or device and often lack standards-based interfaces, most companies have found themselves responsible for many different directories that can't be managed centrally or interoperate easily. Having many incompatible directory services means that:

• End users must use multiple user accounts and passwords to log in to different systems, and they must know the exact locations of information on the network.
• Administrators must understand how to manage each directory within the network and must duplicate many steps when procedures, such as adding a new employee to a company, involve many different directories.
• Application developers must write different logic for every directory that their applications need to access.

In addition to providing comprehensive directory services to Windows applications, Active Directory is designed to be a consolidation point for isolating, migrating, centrally managing, and reducing the number of directories that companies have.
Active Directory acts as a foundation for corporate information-sharing and common management of network resources, including applications, network operating systems, and directory-enabled devices.