Domain Name Registration
A domain name locates an organization or other entity on the Internet. For example, the domain name
locates an Internet address for "mycompany.com.au" at Internet point 22.214.171.124 and a particular host server named "www". The "com.au" part of the domain name reflects the purpose of the organization or entity (in this example, "australian commercial") and is called the top-level domain name. The "mycompany" part of the domain name defines the organization or entity and together with the top-level is called the second-level domain name. The second-level domain name maps to and can be thought of as the "readable" version of the Internet address.
A third level can be defined to identify a particular host server at the Internet address. In our example, "www" is the name of the server that handles Internet requests. (A second server might be called "www2".) A third level of domain name is not required. For example, the fully-qualified domain name could have been "mycompany.com.au" and the server assumed.
Subdomain levels can be used. For example, you could have "www.contact.mycompany.com.au". Together, "www.mycompany.com.au" constitutes a fully-qualified domain name.