A sub-domain is essentially a Website within a Website. A typical sub-domain name would be something like http://HenryCubbage.YouOwnWebsite.Com.

A sub-domain offers a convenient means of setting up a Website in a hurry. If the domain name has existed for a while it will be visible around the world. When a sub-domain is added it is instantly available and there is no cost for registering a new domain name.

So, what is a sub-domain? There are several levels to a domain name.

• The Top Level Domain is a suffix such as .Com or .Net.
• The second level is the site name, such as PlanetEagle.
• The third level is a sub-domain, such as Registry.PlanetEagle.Com.

Let's say Manny, Moe, and Jack want to share a Website with us. We would use the "control panel" on our Web server with set up three sub-domains and have these fellows up and running within minutes. Their complete Web addresses would be:

http://Manny.PlanetEagle.Com
http://Moe.PlanetEagle.Com
http://Jack.PlanetEagle.Com

Notice that there is no "www" ahead of the name. Sometimes you can include it but more often than not the name will be rejected.

The pool of available names is virtually unlimited since each is a sub-set of the second level domain, which is PlanetEagle.Com in this case. It is up to the administrator of the Web server to decide what names to all or disallow.

• Not all Web hosting plans include sub-domains. If you need them, be sure to check with your hosting company before making a commitment.

If these three people wanted to have a Website with their own domain name they could simply register the domain and use domain forwarding to point the domain to their sub-domain Web space on our server.