What is Domain Controller and Active Directory

What is a Domain Controller?

Each employees in A's office has a key to the building. One weekend A forgets her key. The security officer then authenticated her as an employee and lets her in.

You can think domain controller similar to the security officer of above situation. There are many computer in office and each requires users to login with their credentials. If there are hundreds of computers then from the perspective of an Information Technology (IT) professional, it is difficult to manage the authentication of each individual machine. To simply the task what can be done is to configure one computer to manage the authentication of all the others. Now all office computers be connected to this main computer to form a network. The main computer is known as the domain controller, while the other computers it authenticates are known as clients. In such set up, the client computers are said to be on the Windows domain. Now the IT person finds that the login credentials will not have to be managed on each individual computer. instead, the user names and login credentials of all authenticated users in the office can be managed much more easily through one machine, the domain controller.

Active Directory

Active Directory is the central database on a domain controller where the login credentials of all client computers, printers, and other shared resources in the network are stored. When someone tries to login, their login credentials must match those saved in Active Directory. If the login credentials do not match, the user will be denied access. All client computers on the domain share this common Active Directory. Only an administrator or IT professional has authority to add computers or shared resources to the domain, further strengthening security.