A domain controller is a server running Active Directory Domain Services (AD DS), typically on a Windows Server operating system.A domain controller (DC) is responsible for,Authenticating users and computers in a Windows domain.Storing directory data and managing communication between users and domains, including logins, security policies, and permissions.Running Active Directory Domain Services (AD DS), which is a role in Windows Server used to manage the domain’s centralized data.Example,When a user logs in to a computer that is part of a domain, the domain controller checks the username and password through AD DS to ensure they are correct and grants access based on that user's permissions.