What Does Third-Level Domain Mean?
A third-level domain is the next highest level following the second-level domain in domain name hierarchy. It is the segment that is found directly to the left of the second-level domain. The third-level domain is often called a “subdomain”, and includes a third domain section to the URL.
Techopedia Explains Third-Level Domain
For example, in www.mydomain.com, “www” is the third-level domain. The default or the most commonly used third-level domain is “www”. The third-level domain is generally used to mention a certain server inside a company.
