A Fully Qualified Domain Name (FQDN) is sometimes also called an absolute domain name because it contains specific information about the exact location of the domain, relative to the tree hierarchy of the Domain Name System (DNS). The DNS system resolves Internet Protocol (IP) addresses to names of specific domains, and is the standard naming system for any computers connected to the internet. The FQDN system specifies where in the domain structure the particular referenced domain resides.
Therefore the FQDN will show the top-level domain and how it relates to the root domain. For example, in a theoretical domain system, the personal computer of the boss is called bosscomputer, which resides in a domain which is named companydomain. com. Therefore the fully qualified domain name for the personal computer of the boss is bosscomputer. companydomain. com. This is because there may be many different bosscomputers in the world, but there will be only one computer in the world with a FQDN of bosscomputer.
companydomain. com. However, if there is more than one boss in the company, the FQDN system is able to be expanded to deal with this problem. Again, using this example, if there is a boss who is the head of marketing, and another boss who is the head of accounting, then two separate domains can be setup within the companydomain. com architecture to deal with this problem. If a domain is added as marketing, and another added for accounting, then the FQDN of the boss of marketing becomes bosscomputer. marketing.
companydomain. com, and the boss of accounting becomes bosscomputer. accounting. companydomain. com. The beauty of the domain name system, and subsequently the fully qualified domain name system is that it makes naming computers easy, meaningful and independent of physical location. The DNS server which is working in the example above will only need to hold local records for the local domain but will be able to communicate with external DNS servers and will be able to differentiate the two bosscomputer machines.