Microsoft Active Directory is a directory service for organizing user accounts, servers and client operating systems. Additionally it provides helpful features like enforcing password policies, running login scripts, applying user account restrictions and much more.
Active Directory (AD) is a directory service developed by Microsoft for Windows domain networks. It is included in most Windows Server operating systems as a set of processes and services. Initially, Active Directory was used only for centralized domain management. However, Active Directory eventually became an umbrella title for a broad range of directory-based identity-related services.A server running the Active Directory Domain Service (AD DS) role is called a domain controller. It authenticates and authorizes all users and computers in a Windows domain type network, assigning and enforcing security policies for all computers, and installing or updating software. For example, when a user logs into a computer that is part of a Windows domain, Active Directory checks the submitted username and password and determines whether the user is a system administrator or normal user. Also, it allows management and storage of information, provides authentication and authorization mechanisms and establishes a framework to deploy other related services: Certificate Services, Active Directory Federation Services, Lightweight Directory Services, and Rights Management Services.Active Directory uses Lightweight Directory Access Protocol (LDAP) versions 2 and 3, Microsoft's version of Kerberos, and DNS.Robert R. King defined it in the following way:"A domain represents a database. That database holds records about network services-things like computers, users, groups and other things that use, support, or exist on a network. The domain database is, in effect, Active Directory."