What is "active-directory"

Active Directory (AD) is a directory service on Windows networks.

Directory service is a set of Attributes on existing resources and services in the network, it means it is a way to organize and simplify access to your network resources by centralizingos; as well as, enhance security and give protection to database objects against intruders, or control access of internal network users.

Active Directory maintains data such as user accounts, printers, groups, computers, servers, network resources, etc. It can be fully scalable, increasing as we need it.

sources: Technet, wikipedia