What is Domain Controller?

A domain Controller is a windows server Machine that runs Active Directory Domain Serices.

A "domain" is, to put it simply, a unified collection of machines and user accounts managed by server machines designated as "domain controllers". (This is, of course, an incomplete definition, but it is a good start.)

A domain controller is a computer running one of Microsoft's server operating systems, such as Windows Server2008 or Windows Server2008 R2 in any edition except Web Edition, or one of the small business-oriented server products

domain controller is the server that holds the Active Directory service. in the network.

A domain controller is the centerpiece of the Windows Active Directory service. It authenticates users, stores user account information and enforces security policy for a Windows domain.

The Domain Controller is the heart of Active Directory. It's Microsoft Directory Service Holder, means it holds the Active Directory Database that contains shared networked resources in an interprise environment. Shared networked resources like computer and user accounts and maybe published printers, also all groups that may have other accounts as members. No one can access any domain resources without contacting a Domain Controller.

A Domain Controller is a Server Running Window Server and has Active Directory role and responsible for allowing domain computer to access Resourece in your enterprise Netwok  it basically hold Active Directory of the Organization which is a databse which hold users Account, group, organizational unit

when a user want to access a resourec like file Server, Printer inside the organization that user must contact Domain controller for permission to access only user can accesss resource and login to the device if they are granted by the domain controller

so basically it is a central location to manage Security (Permission), user account and lot of thing can be managed

Domain controller is a server which contain matching copies of the user accounts and other active directory data.

A Domain Controller is a server that holds the Active Directory Database. This database is a repositary of User informations, Domain attributes, schema details on the domain structure. Now a domain controller is a machine that needs to run a Server edition of Windows (Windows2000 Server, Windows Server2003/2008/2008 R2, etc. Again, in a domain there can be more than one Domain controller, and these domain controllers communicate and replicate information amongst each other to ensure consistency.

A Domain controller could also hold DNS data (Active Directory Integrated Zones), which also assists in name resolution.