In addition to the top-level domains, there are second-level domain (SLD) names. These are the names directly to the left of .com, .net, and the other top-level domains. As an example, in the domain mbah.bilank.org, "bilank" is the second-level domain.
On the next level are third-level domains. These domains are immediately to the left of a second-level domain. In the mbah.bilank.org example, "mbah" is a third-level domain.
Domains of third or higher level are also known as subdomains, though this term technically applies to a domain of any level, since even a top-level domain is a "subdomain" of the "root" domain (a "zeroth-level" domain that is designated by a dot alone).
On the next level are third-level domains. These domains are immediately to the left of a second-level domain. In the mbah.bilank.org example, "mbah" is a third-level domain.
Domains of third or higher level are also known as subdomains, though this term technically applies to a domain of any level, since even a top-level domain is a "subdomain" of the "root" domain (a "zeroth-level" domain that is designated by a dot alone).