What is the Third Level Domain?

[joellee]

A third-level domain is the section of a domain that is present to the left of the dot of a second-level domain (SLD).  For example, .CO.IN is a country code second-level domain (ccSLD) under the .IN country code top-level domain (ccTLD). The .IN registry supports domain registration under .CO.IN with ".CO.IN" serving as the domain extension. For example, someone owns Example.CO.IN, so the third-level domain is “Example”