Each name server is responsible for maintaining the master record of the information associated with certain domain names. In practice, things are more complicated than this description implies. This is known as propagating new domain name information. If you move a domain name, you are basically transferring the right to maintain the association between that domain name and its IP address to a different name server. This is often necessary, for instance, when changing web-hosting companies.
Every domain name is registered under a top domain of some kind.
The top domain is often referred to as the domain extension. In accordance with the increase of Internet users there has been an increase in domain registrations. This, due to the fact that in 1998 the United States Department of Commerce amended its policy and allowed the ability to register a domain to more that one company. In order to establish a web site, a company should first decide on a domain name. The company should then log on to one of the registration companies and submit its suggested name.