Is there any difference between Domain controller and Active directory?

If I want to define domain controller then i would say DC is where active directory installed or

Acitve Directory simply means: Secure centralized authentication and management
and domain controller = ADDS + DNS.

But I get confused when i read here that

I also think it is VERY EASY to say DOMAIN CONTROLLER == ACTIVE
DIRECTORY, which isn't quite the case.

I want to know is it correct or wrong? If wrong then what is the difference?

Answer

Just to put it another way that might be helpful is to say that Active Directory is a directory service for Windows domain networks and the Domain Controller is what serves that service on your Windows domain network. So, there is a difference between Active Directory and Domain Controller. One is the service, while the other is what serves that service.