A subdomain is a second website, with its own unique content, that is hosted on a subdirectory of a primary domain. For example, if the primary domain is "example.com", a subdomain could be "subdomain.example.com". Subdomains are often used to organize and categorize different sections of a website, or to create separate websites for different purposes or audiences.
For example, a company might use a subdomain for their blog, or for a specific product or service. Subdomains are created and managed through the domain name system (DNS) of the primary domain.
