This article provides a guide for dealing with a fully qualified domain name (FQDN).
Fully Qualified Domain Names
An FQDN, or a Fully Qualified Domain Name, is written with the hostname and the domain name, including the top-level domain, in that order: [hostname].[domain].[tld].
An FQDN might also be called an "absolute domain name" since it provides the absolute path of the host.
Fully Qualified Domain Name Examples
A fully qualified domain name is always written in this format: [hostname].[domain].[tld]. For example, a mail server on the example.com domain may use the FQDN mail.example.com.