Domain

Every URL contains a domain name, each of which is unique within the entire Internet.

When a person or company purchases a domain name, they are buying the combination of the top level domain (.com, .net, .org, .co.uk, .de, etc.) and the second level domain name (google, yahoo, amazon, etc). The "www" section is commonly called the "sub domain" or, more technically, the third level domain.

The owner of a domain name can choose to use the most commonly used sub domain "www" or any other name they want. For example, they could have a sub domain of uk.google.com or they could have no sub domain name at all (google.com); it all depends on how the company and their system administrator wish to set up their web site.

Note: Each part of a domain is separated by a dot, and at the end of the domain is a forward slash ( / ).

Examples:

www - Sub domain (third level domain)

google - Domain (second level domain)

com - Top level domain

www.google.com - Full domain