Active Directory is a Directory Service created by Microsoft. It is included in Windows Server operating systems since Windows 2000 Server, which was launched in 2000.
Almost all Active Directory installations actually include several separate but related components; although the term “Active Directory” technically refers only to the directory service, in general use it refers to the entire constellation of parts.
Active Directory is primarily used to store directory objects (like users and groups) and their attributes and relationships to one another. These objects are most commonly used to control access to various resources; for instance, an Active Directory might contain a group which grants its members permission to log into a certain server, or to print to a specific printer, or even to perform administrative tasks on the directory itself.
Active Directory also provides a useful configuration management service called Group Policy, which can be used to manage computers which connect to the domain in order to install packages, configure software, and much more.
Most Active Directory installations have a few distinct parts which all work together:
Also, Active Directory is designed in such a way that it can be run on multiple computers at the same time, which coordinate between themselves to ensure that their data is always consistent; this process is called “replication”.