Active Directory (AD) is a directory service created by Microsoft for Windows domain networks. It provides a central location for network administration and security.
An advanced, hierarchical directory service that comes with Windows servers and used for managing permissions and user access to network resources. Introduced in Windows 2000, Active Directory is a domain-based network that is structured like the Internet's Domain Naming System (DNS). Using the LDAP directory access protocol, a company's workgroups (departments, sections, offices, etc.) are assigned domain names similar to Web addresses, and any LDAP-compliant Windows, Mac, Unix or Linux client can access them.