This page allows the server administrator to create the default settings for allowing virtual site administrators to create subdomains.
A subdomain is used to create an a “sub-site” on an existing virtual site. A subdomain shares quota and ownership permissions with the virtual site under which it is created. Subdomains are available using a hostname that is different than the primary or alias hostnames of a virtual site.
For example, if you have a site using hostname www and domain foo.com, your site is www.foo.com. In most cases you will also have configured an alias on that site for just the domain (foo.com). Now let's say you want to configure new content that will be available via a different hostname that contains different content than the main virtual site. You can configure a subdomain for this purpose.
Allows you to enable Sub Domains for virtual hosts
Allows you to create a baseline of the default each site can create