The INTERNET:
The Internet is actually millions of computers connected together in some way (phone lines, Ethernet, ISDN, cable modems) so that they can share information. The Internet is really one big network of computers. All of the things that people think of when they hear about the Internet, such as email the World Wide Web, File Transfer Protocol, etc. are types of information that are shared by computers on the Internet.
INTRANETS:
Intranets are internet-based networks that are within a company, usually a corporation, in order to share and exchange information. It is accessible only by the organization's members, employees, or others who have authorization.
EXTRANETS:
Extranet is an intranet that is partly accessible to authorized outsiders and it also provides many levels of accessibility. One can only access an extranet only you have a valid user name and password and that determines which part of the extranet you can view. An example of the integration of a company Extranet is EDI. (Electronic Data Interchange)
EXAMPLES OF ORGANIZATIONS THAT UTILIZE ALL THREE SCENARIOS:
*Komatsu America International Co - Utilizes the Internet to feature its product lines, provide company news and financial data. The company also utilizes a Cisco based company Intranet for internal data storage and an Extranet primarily for the purposes of EDI.
*US West - Utilizes the Internet to reach its various levels of customers, provide news about products and services and ways to contact the company. The company uses an Intranet for internal communications and an Extranet Hub to allow Intranet access to their various outside consultants, suppliers and contract employees.
*Ford Motor Company - Ford Motor