What is domain name?
A domain name is the title assigned to sites on the Web.
All Web sites, every single one of them, have domain names. These domain names are present in the formal Web address (the mess beginning with http that you type into your Internet browser to look at online pages), and that's from where most of the confusion springs.
The domain name is the first point of your website that people see before they even click through to your URL.
When your site shows up, in the search engines or as a link on another site, your
domain name will tell people what the site is about.
Every page belonging to this domain will contain the name; you see this all the time with sites like Google, Yahoo or even eDomain. All pages on the Internet are part of someone's domain.