What is Active Directory (AD)? 

Active Directory (AD) is a proprietary directory service from Microsoft. It records data on users, devices, applications, groups, and devices in a hierarchical structure. AD has become an umbrella term for a broad range of directory-based identity-related services on Windows systems. It’s also called a domain controller and authenticates and authorizes users and devices in a Windows domain.

What is Active Directory (AD) used for? 

AD allows for managing and storing identity data and provides authentication and authorization services for connected systems, applications, and networks. AD allows administrators to organize objects of a network, like users, computers, and devices, into a hierarchical collection of containers. Many Windows-based companies use AD to store identity data and manage access to applications, systems, services, and more.