Definition: AD DS is one of the main services provided in Active Directory (AD). Interactions of the users with any network resource are managed by AD DS. That means it is responsibility of AD DS to check the permission of the user, when the user logs into any network resource (computer, printer, network drive, etc...).

AD DS also provides method of storing Directory Data and making these data available to the users and administrators in the domain.

• Microsoft products like, Exchange Server, Outlook, Skype, SharePoint Server rely on AD DS to provide resource access.
• The server that hosts AD DS is called Domain Controller.

NOTE: Active Directory (AD) only stores the data and (AD DS) provides ways to manipulate and access data from AD. So AD is a storage system and AD DS is a service within AD that works around that storage system.