Alternatively referred to as a namespace, a domain namespace is a name service provided by the Internet for Transmission Control Protocol networks/Internet Protocol (TCP/IP). DNS is broken up into domains, a logical organization of computers that exist in a larger network. Below is an example of the hierarchy of domain naming on the Internet.
In the above example, all websites are broken into regional sections based on the TLD (top-level domain). In the example of http://support.computerhope.com it has a ".com" TLD, with "computerhope" as its second level domain that is local to the .com TLD, and "support" as its subdomain, which is determined by its server.
Those who are setting up their own network can also create private networks with their own domain namespaces.