What is Active Directory?

Active Directory is a database that keeps track of all the user accounts and passwords in your organization. It allows you to store your user accounts and passwords in one protected location, improving your organization's security. 

Active Directory (AD) is a directory service created by Microsoft for Windows domain networks. It is included in most Windows Server operating systems. Server computers on which Active Directory is running are called domain controllers.

Active Directory serves as a central location for network administration and security. It is responsible for authenticating and authorizing 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. For example, when a user logs into a computer that is part of a Windows domain, it is Active Directory that verifies his or her password and specifies whether he or she is a system administrator or normal user. 

Active Directory is subdivided into one or more domains. A domain is a security boundary. Each domain is hosted by a server computer called a domain controller (DC). A domain controller manages all of the user accounts and passwords for a domain.