A aubdomain is created off a virtual domain name. sub domains can point to sub-directories of your main account. If you sign your sites with an unlimited web hosting company like Hostony or Hostgator, you can utilize the facility to create unlimited subdomains for each of your domain.

For instance, for each of your website you can create:

http://article.domain.com

http://ebook.domain.com

http://directory.domain.com

etc…

Although you will never need to create subdomains in unlimited numbers, this feature can be very beneficial. For instance, you can create subdomains to install various scripts such as Amazon Store Manager and Link Directory in order to enhance the functionality of your websites.

In addition, you can use subdomains to redirect visitors to other websites. If you use your website to promote five different affiliate programs, you can create a Subdomain for each of them to perform redirection. This way, your affiliate URLs will look more proffessional.

With Hostony and Hostgator you can even setup password protected folders and FTP accounts to enable your family or friends to access your subdomains.