It seems like the techno-geniuses who named the various computer-related applications online got together and deliberately made the names as similar as possible just to confuse and scare those of us who are not techno-geniuses.

But, the names actually make sense if you know the difference between the three.

Net is the short form of network. The Internet, intranets and extranets refer to different types of computer networks where different computers are somehow linked together. If you like language, remembering the Latin meanings for the prefixes "inter'', "intra'' and "extra'' will help.

Let's start with the one that is used the most -- Internet.

The Latin prefix "inter'' means "between''. So the Internet is just a network that allows for connections between computer networks, and according to the official definition of the Webopaedia, he Internet, is "a global network connecting millions of computers.'' The Internet grew out of an experiment begun in the 1960s by the US Department of Defence, which wanted to create a computer network that would continue to function in the event of a disaster, such as a nuclear war. If part of the network was damaged or destroyed, the rest of the system still had to work.

That network was the so-called ARPANET, which linked US scientific and academic researchers. It was the forerunner of today's Internet. In 1985, the National Science Foundation (NSF) created NSFNET, a series of networks for research and education communication. Based on ARPANET protocols, the NSFNET created a national backbone service, provided free to any US research and educational institution. At the same time, regional networks were created to link individual institutions with the national backbone service. Then corporations such as Sprint and MCI began to build their own networks, which they linked to NSFNET.

According to the latest statistics from Commerce Net, there are 249 million Internet users worldwide in over 100 countries. Because your computer is able to go online, your computer is part of the Internet.

If you have online access at work or at school, those computers are also part of the Internet. No one owns the Internet, it just forms connections between all the different computers and computer networks worldwide.

What about an Intranet? The Latin prefix "intra'' means inside, so by extension an intranet should refer to a computer network inside of an organisation, which it does. An Intranet is a private network belonging to an organisation, usually a corporation, accessible only by the organisation's members, employees, or others with authorisation. In essence, it's like a mini, private version of the Internet. An Intranet's Web sites look and act just like any other Web sites, but the Intranet is set up using what is called a firewall, which prevents unauthorised access from outsiders. Like the Internet itself, Intranets are used to share information that needs to be quickly and easily disseminated, such as in-house newsletters or announcements, company policies, phone lists, and applications. Intranets can also contain training procedures, inventory lists, and payroll information.

Virtually any information that needs to be sent within a corporation can be sent via its Intranet.

The Latin prefix "extra'' means outside, and an Extranet is just a fancy way of saying that a corporation has opened up portions of its Intranet to authorised users outside the corporation. Many public companies allow stockholders to view their financials this way, for instance. Typically, Extranet users are given a login name and password, which tells the computer specifically what information they are entitled to view.

Extranets are becoming more and more popular as more companies are discovering their potential. Want your customers to place their own orders? Wish you could check your grades without making the trip back to school? Would you like to show your client the plans without using overnight mail? All this and more is possible with an Extranet.

That's it! It really does all make sense once you get the hang of it and there really was a reason for your teacher making you memorise all those Latin prefixes in school.