A subdomain is a part of a larger domain used to organize or separate content within the website. It appears before the root domain in a URL, separated by a dot, like, blog.example.com.

Subdomains are unique addresses under a root domain. For example, blog.example.com and shop.example.com are distinct from each other and example.com.

Cookie Information differentiates domains and subdomains. Subdomains are unique.

If you have a website on the domain http://www.example.com and a support page on http://www.support.example.com, they are two unique domains.