Fully-Qualified Domain Names

A domain name is said to be fully-qualified when it includes the names of every DNS domain from the local domain on up to ".", the DNS root domain. Conceptually, the fully-qualified domain name indicates the path to the root, as does the absolute path name of a UNIX file. However, fully-qualified domain names are read from lowest, on the left, to highest, on the right. Therefore, a fully-qualified domain name has the syntax:

The fully qualified domain names for the ajax domain and its subdomains are:

ajax.com. 
sales.ajax.com 
test.ajax.com. 
manf.ajax.com

Note the dot at the furthest right position of the name.