A fully qualified domain name consists of a host and domain name, including top-level domain. For example,
www.techwarelabs..com is a fully qualified domain name. www is the host, techwarelabs is the second-level domain, and.com is the top level domain.
A FQDN always starts with a host name and continues all the way up to the top-level domain name, so
www.devel.techwarelabs.com is also a FQDN.