FQDN – Fully Qualified Domain Name

What is exactly the meaning of the term Fully Qualified Domain Name (FQDN). I was thinking that www.webplay.pro is a FQDN for example. While reading the great book Pro DNS and BIND 10 By Ron Aitchison I found out that technically an FQDN unambiguously defines a domain name to the root and therefore must terminate with the normally silent dot.

So the valid FQDN for www.webplay.pro domain is:

www.webplay.pro.