4 part domain names

[Chad Leigh -- Shire.Net LLC]

the "zone" description listed was pretty good.

Basically, the leftmost name in a fully qualified domain name is the 
"host" (which could really be an alias or something) and the rest is 
the domain name.  So for example

u17.us.mail.somecompany.com

u17 is the "host" (in this fictional account, a departmental mail 
server in the US division of somecompany)

us.mail.somecompany.com  is the "domain"

The names get more general from left to right.  It is a hierarchy.

Similar to a postal address.

For example

John Doe
17 Main Street
Anytown, TX  75263
USA

John Doe is the "host"

17 is a specific location on a general street "Main Street" which is 
found in Anytown which is found in TX which is found in the USA.  As a 
domain name it might be written

JohnDoe.17.MainStreet.75263.Anytown.TX.USA


Alfons Mueller
Schardthof 10
D-84051 Essenbach
Germany

would be the same.

AlfonsMueller.10.Schardthof.84051.Essenbach.Bayern.Germany

is a progressively more general description of where Mr. Alfons Mueller 
can be located.

When you send a postal letter to one of these people (John Doe or 
Alfons Mueller), the letter is sent to the respective country's main 
postal "office", then to a regional and then a city and then maybe a 
neighborhood (depending on your area) post office before being 
delivered.  The hierarchy helps the routing of the mail.

Same with domain names.  The hierarchy helps to keep trach of the 
complexity in a delegated fashion

Sorry for the complex examples
Chad