Subdomain

A subdomain is a prefix added to your domain to create a distinct address under it — blog.example.com, app.example.com, or mail.example.com are all subdomains of example.com. You create one by adding a DNS record (usually an A or CNAME) at the nameservers for the parent domain, with no extra registration or fee. Subdomains let one registered name host many services, which is why they are a building block for sites, apps, and APIs. In the tokenized world, ownership lives at the registered second-level domain; subdomains are configuration under it and follow whoever controls the parent's wallet. Sources: RFC 1034; Cloudflare subdomain glossary.