Active Directory is a directory service

Directory service

A directory service is the software system that stores, organizes and provides access to information in a directory. In software engineering, a directory is a map between names and values. It allows the lookup of values given a name, similar to a dictionary...

 created by Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 for Windows domain networks. It is included in most Windows Server

Windows Server

Windows Server is a brand name for a group of server operating systems released by Microsoft Corporation. All are part of Microsoft Servers.- Members :This brand includes the following software:* Windows 2000 Server* Windows Server 2003...

 operating systems. Server computers on which Active Directory is running are called domain controller

Domain controller

On Windows Server Systems, a domain controller is a server that responds to security authentication requests within the Windows Server domain...

s.

Active Directory serves as a central location for network administration and security. It is responsible for authenticating

Authentication

Authentication is the act of confirming the truth of an attribute of a datum or entity...

 and authorizing

Authorization

Authorization is the function of specifying access rights to resources, which is related to information security and computer security in general and to access control in particular. More formally, "to authorize" is to define access policy...

 all users and computers within a network of Windows domain type, assigning and enforcing security policies for all computers in a network and installing or updating software on network computers.