Subdomains are part of your main domain that you can forward to URLs or point to IP addresses and directories within your hosting account.
Itís easy to create a memorable Web address for unique content areas of your site by using sub domains. For example, you could create a subdomain for pictures on your site called "pics" that is accessible through the URL pics.coolexample.com in addition to www.coolexample.com/pics.
You can add up to 100 sub domains per domain name. You can also add multiple levels of sub domains. For instance, you can add info.blog.coolexample.com to delve into an even more specific area of interest on your site. Each subdomain can be up to 25 characters long.