The domain name is the unique name that identifies an Internet site. The Internet is made up of hundreds of thousands of computers and networks, all with their own domain name or unique address. Domain names always have two or more parts separated by dots. A given server may have more than one domain name, but a given domain name points to only one server.

For example, whitehouse.gov is the domain name belonging to the White House computer system. Once a system administrator registers a unique domain name, subaddresses can be assigned to the machines and people on the local network. Thus, the President's e-mail address is president@whitehouse.gov, the Vice-President's is vice-president@whitehouse.gov, and so on.