What Does Fully Qualified Domain Name (FQDN) Mean?
A fully qualified domain name (FQDN) is a domain name that specifies not only its top-level domain and parent domain name, but also its local host. These more specific domain names reveal additional information about the origin of a Web page in the actual uniform resource locater (URL).
Techopedia Explains Fully Qualified Domain Name (FQDN)
The idea behind a fully qualified domain name is that it deals with the ambiguity in some domain entries. Unless each piece of information is specified, a browser or other system may not be able to accurately locate a destination. In some ways, having a fully qualified domain name is similar to having a fully qualified PC-DOS command for locating a single file or folder in the hierarchical data storage system of a conventional personal computer. The fully qualified domain name is a reference to a new resource for allowing specific access to resources over the global Internet.
One issue with a fully qualified domain name involves the resolution of these domain entries. Organizations like the Internet Engineering Task Force have identified specific resolution processes for fully qualified domain names in order to help establish consistent communications.