The Internet is the worldwide network of networks, which is available to business, government, education, and individuals. Many different services are provided over the Internet, including electronic mail, instant messaging and web applications. Single devices and entire local networks can join the Internet and become connected worldwide at a variety of speeds. Many large telecommunications companies carry the backbone of the Internet. The Internet “provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein.” [1]

An “intranet is a private network inside a company or organization that uses the same kinds of software that you would find on the public Internet, but that is only for internal use. An intranet may be on the Internet or may simply be a network.” [2] I have found that Intranet and internal web are often interchanged, as well as Intranet and internal network. I think in general it is safe to refer to the all services available within the private networking domain of the organization. The Intranet of a company is often available by plugging into the network at a business office or virtually plugging in to it through remote Virtual Private Network access.

I have found several overlapping definitions of Extranet, but in general they all refer to the same concepts. An Extranet is a company provided extension of its Intranet services to customers and business partners. [3] Using Amazon as an example, they do business over the Internet with the majority of people with a web application. They also have business partners that receive orders and provide special services to Amazon’s customers. Business partners have access to Amazon’s Extranet, which allows them to interact with the private portion of the business’ network services, but only those services Amazon allows.

[1] http://www.cs.columbia.edu/~hgs/internet/definition.html
[2] http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/Glossary.html
[3] http://elab.vanderbilt.edu/research/studentprojects/extranet/execsumm.html
[4] http://elab.vanderbilt.edu/research/studentprojects/extranet/extranet.html