From http://www.w3schools.com (Copyright Refsnes Data)
A Domain Name is a unique name for your web site.
Choosing a hosting solution should include domain name registration.
Your domain name should be easy to remember and easy to type.
A domain name is a unique name for a web site, like w3schools.com.
Domain names must be registered. When domain names are registered they are added to a large domain name register, and information about your site - including your internet IP address - is stored on a DNS server.
DNS stands for Domain Name System. A DNS server is responsible for informing all other computers on the Internet about your domain name and your site address.
Domains can be registered from domain name registration companies such as http://www.dotdnr.com.
These companies provide interfaces to search for available domain names and they offer a variety of domain name extensions that can be registered at the same time.
Domain Name Registration provides registration services for .com .net .org .biz .info .us .nu .ws .cc and .tv domains.
Newer domain extensions such as .biz .info and .us have more choices available as many of the popular domains have yet to be taken. While .com and .net domains are well established and recognized, most popular domains with these extensions are already registered.
Choosing a domain is a major step for any individual or organization.
While domains are being registered at a record, new domain extensions and creative thinking still offer thousands of excellent choices. When selecting a name it is important to consider the purpose of a domain name, which is to provide people an easy way to reach your web site. The best domains have the following characteristics:
Short - People don't like to type! The shorter your domain, the easier it is to reach and the less are the chance the user will make a typographical error while typing it.
Meaningful - A short domain is nothing without meaning, 34i4nh69.com is only 8 characters long but would not be easy to enter or remember. Select a domain that relates to your site in a way that people will understand.
Clear - Clarity is important when selecting a domain name. You should avoid selecting a name that is difficult to spell or pronounce. Also, pay close attention to how your domain sounds and how effectively it can be communicated over the phone.
Exposure: Just like premium real-estate on the ground that gets the most exposure, names that are short and easy to remember are an asset. In addition to humans viewing your domain, you should consider search engines. Search engines index your site and rank it for relevance against terms people search for online. In order to maximize your sites exposure, consider including a relevant search term in your domain. Of course, this should only be considered if it still maintains a short, clear and meaningful domain.
Most people are unaware but they already use sub domains on a daily basis. The famous "www" of the World Wide Web is the most common example of a sub domain. Sub domains can be created on a DNS server and they don't need to be registered with a domain registrar, of course, the original domain would need to be registered before a sub domain could be created. Common examples of sub domains used on the internet are http://store.apple.com and http://support.microsoft.com.
Sub domains can be requested from your web hosting provider or created by yourself if you manage your own DNS server.
Some providers will offer you a unique name under their own name like: www.theircompany.com/yourcompany/
This is not a real domain name, it is a directory - and you should try to avoid it.
These URLs are not desirable, especially for companies. Try to avoid them if you can afford to register a domain. Typically these are more commonly used for personal sites and free sites provided by your ISP, you may have seen www.theircompany.com/~username as a common address, this is just another way to share a single domain and provide users their own address.
Open competition in domain name registration has brought about a dramatic decrease in pricing so domain sharing is far less common since people can register their own domains for only $15 per year.
Another source for domain registrations is expired domains. When you register a domain, think of it as a rental, assuming there are no legal or trademark issues with the domain name, you are free to use it as long as you continue to pay the yearly fee (you can now also register in advance as many as 10 years). Some people register domains as speculators, hoping that they can later sell them, while others may have planned to use a domain and never had the time. The result is that domains that were previously registered regularly become available for registration again. You can see, and search through a list of recently expired domains for free at http://www.dotdnr.com. If you wish to register an expired domain you pay the same fee as you would for a new registration.
After you have chosen - and registered - your own domain name, make sure you use it on all your web pages and on all your correspondence, like email and traditional mail.
It is important to let other people be aware of your name, and to inform your partners and customers about your web site.
DotDNR offers .com .net .org .ws .cc and .tv domains for as little as $15 per year.
In addition, you can transfer your domain to DotDNR and add a full year to your existing registration for only $15. Save $20 or more over other major registrars.
International domain name registration is also offered.
From http://www.w3schools.com (Copyright Refsnes Data)