Definition: A subdomain is a domain hosted on its parent domain, much like the parent is a subdomain of the Top Level Domain, such as com, org, and net.
Purpose of Subdomains
Subdomains have served a large variety of purposes. Mainly as hosting of different services, and this still remains one of their main uses today.
Some websites use the www subdomain to host their website on, while other websites uses the main domain. Some websites might also use subdomains to host multiple versions of their website, such as an English version on the en, and a Danish version on the da subdomain.
How subdomains works
A Subdomain is the first part of the URL, found before the parent domain.