- See also: How to Create Subdomain Pages
A subdomain is a domain that is part of another bigger domain. For example sub.domain.com is a subdomain where domain.com would be the domain.
By nature, they didn't last as long as the main website/parent domain, and therefore making each page about them is considered to be a futile effort, because one could create as many subdomains as one would and delete them on the next day.
Many internet services also provide a way for each registered user to make their own subdomain in the website (such as yourusername.aboutus.org) and very few of them are really worth our notice, therefore only create subdomain pages where it really necessary . Unworthy ones will be deleted by our cleanup processes.