Domain name is an easy-to-remember address that can be translated by DNS into server's IP address ,and they are the unique name that identifies an Internet site.

Domain names are hierarchical. Domain's suffix indicates which TLD (top level domain) it belongs to, for example .com, .gov, .org, .net, or .jp. Recently ICANN (Internet Corporation for Assigned Names and Numbers) added several new TLDs, like .biz, .pro., and .museum. A given machine may have more than one Domain Name but a given Domain Name points to only one machine.

For example, the domain names: xtraorbit.com, ftp.xtraorbit.net, whatever.xtraorbit.net can all refer to the same machine, but each domain name can refer to no more than one machine. It is also possible for a Domain Name to exist but not be connected to an actual machine. This is often done so that a group or business can have an Internet e-mail address without having to establish a real Internet site.

In these cases, some real Internet machine must handle the mail on behalf of the listed Domain Name.