Domain:

Domain refers to the last few letters in a web address. You can tell a lot from a domain as it specifies whether the web site is a certain type of organization or from what country it originates. For example, .com sites are commercial, .edu represents an educational institution in the U.S, .org is usually a non-profit organization, .ca is for a Canadian web site, and addresses with .cn are from China.

For example:
   .com - commercial business
   .org - organizations
   .ca - Canada
   .cn - China
   .uk - Britain
   .au - Australia
   .mil - US Military
   .edu - US educational instituitions