Domain Names Specifics
A domain name is an Uniform resource locator (URL), otherwise known as a host name. Domain names are used to identify a website and link to its files in a human friendly format. All domain names are comprised of at least 2 parts, a top level domain (TLD) and a second level domain(SLD) separated by a period. There can be numerous more lower level domains, each separated by a period and to the left of the next higher level domain.
Top level domains are to the far right of the host name, such as ".com" in "example.com" and are usually three letters long. There are many different types of top level domains such as ".com", ".org", ".net", ".edu" and ".biz" to name a few.
The second level domain is the part just to the left of the "dot" or period, such as "example" in "example.com". A sub domain is an example of a lower level domain, such as "contact.example.com". Sub domains don't cost anything extra and need not be registered formally but are created by specifying them within your domain control panel.
Domain names have to be registered annually with a domain name registrar. When you register a domain name you are actually registering a top level and second level domain. The domain name is the property of the registerer until relinquished through non-renewal or sold.
Domains names are registered with the Domain Name System(DNS) to associate the domain name to a web servers IP address. This allows the easy to use of human readable domain names instead of requesting a web site by its IP Address.
Domain name registration varies in price but usually costs between $10-$20 a year. Many web hosting companies will provide you with free domain name registration with web hosting plans for anywhere from the first year to as long as you host your site with them.