A domain Controller is a computer that is running Windows NT Server 4.0 or Windows 2000 Server or Windows server 2003 operating system. Also Active Directory must be installed in both Windows 2000 Server and Windows Server 2003.
Domain Controller stores read-write copy of the domain database. Domain Controllers manage communication between users and domains,including user logon processes,authentication and directory searches. They store directory data and synchronize directory data using multimaster replication,ensuring consistency of information over time. Active Directory supports multimaster replication of directory data between all domain controllers in a domain.
A Member Server is a computer that is running Windows NT Server 4.0 or Windows 2000 Server or Windows Server 2003 operating system. But Active Directory is not installed in both Windows 2000 Server and Windows Server 2003. A member server belongs to a domain but it is not a domain controller.
They can operate as file servers,application servers,webservers,database servers,firewalls,certificate servers and remote access servers. They does not process network account logons,participate in active directory replication,store domain security policy information.
By installing Active Directory we can promote a member server to a domain controller. Also we can demote a domain controller to a member server by uninstalling Active Directory.
Stand Alone Server:
A Stand Alone Server is a computer that is running Windows NT server 4.0 or Windows 2000 Server or Windows Server 2003 operating system but it is not a member of a domain. It is a member of a workgroup. These servers can share resources with other computers on the network.
Note: Articles on Windows NT,Windows 2000 Server,Windows 2003 Server will come soon on my blog under the same NETWORKING section.