Active Directory is Microsoft's directory service that allows centralized management of user access and policies. It provides a single location for user information and authentication. Using Active Directory provides benefits such as simpler administration, security, scalability, and standardization. Active Directory can integrate with other Microsoft services like Exchange, SharePoint, and Lync to enable single sign-on and easy profile management across services. Windows Server Active Directory also supports identity and access management in the cloud and hybrid environments through integration with Azure Active Directory. It allows extending on-premises Active Directory to the cloud and provides single sign-on for cloud applications.