http://www.kloth.net/services/whois.php

Query this WHOIS service to look up internet domain name information. This online web tool works for generic top level (gTLD) domains .COM/.NET/.ORG/.BIZ/.INFO and many (most) other national ccTLD (country code TLDs) domain names by sending a realtime query to specific domain registry whois servers.

Just enter SLD.TLD (top level and second level domains), no "WWW" or other sub-domain data (example: enter example.com, not www.example.com).
Sometimes a further sub-domain prefix is required (example: example.co.uk).
If you are looking for the owner of a specific IP address, just enter the IP V4 address (example: 10.22.33.44).
To look up a net handle, enter the handle (example: NET-10-22-33-0-1).
To find out about an autonomous system number, enter the ASN (example: AS23456).
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http://searchwindevelopment.techtarget.com/sDefinition/0,,sid8_gci211988...

a domain name locates an organization or other entity on the internet. for eg, the doamain name
www.totalbaseball.com

locates an internet address for "totalbaseball.com" at internet point 199.0.0.2 and a particular host server named "www". The "com" part of the domain name reflects the purpose of the organizatioin or entity (in this example, "commercial") and is called the top-level domain name. the "totalbaseball" part of the domain name defines the organization or entity and together with the top-level is called the second-level domain name. the second-level domain name maps to and can be thought of as the "readable" version of the interner address.
A third level can be defined to identify a particular host server at the interner address. In our example, "www" is the name of the server that handles interner requests. (a second server might be called "www2".) a third level of domain name is not required. for example, the fully qualified domain name could have been "totalbaseball.com" and the server assumed.

subdomain levels can be used. for eg you could have "www.nyyankees.totalbseball.com". together, "www.totalbaseball.com" constitutes a fully-qualifird domain name.

second level domain names must be unique on the interner and registered with one of the ICANN accredited registrars for the com, net, and org top level domain.