Your Internet Consultant - The FAQs of Life Online
To the technically-minded, the Internet is a network of computer networks that talk to each other using Transmission Control Protocol/Internet Protocol (TCP/IP). TCP/IP is a set of rules that define how messages can be sent between computers. A communications protocol allows different kinds of computers using different operating systems to communicate with each other. That is important because the Internet isn't made up of any single type of computer system. Using TCP/IP, hundreds of different types of computers are able to communicate on the Internet.
This common set of protocols makes it possible for a user plugged into any network on the Internet to communicate with people or software located on any of the other networks connected to the Internet.
The Internet started as a single network, the ARPANet (the U.S. Department of Defense Advanced Projects Research Agency Network), but it now encompasses about 10,000 other networks of all sizes around the world, including the National Science Foundation Network (NSFNET), the Australian Academic and Research Network (AARNet), the NASA Science Internet (NSI), and the Swiss Academic and Research Network (SWITCH).
To most of the people who use the Internet, the Net isn't about networks, protocols, and operating systems; it's a community of people. A very large community. I might even call it (with a cringe for using such a trite, hackneyed term) a "global village."
The Internet is a locale, a place. It is the closest thing we've got to "Cyberspace" (a term coined by William Gibson in his science fiction classic Neuromancer), an electronic place where people and programs work, learn, and coexist (sometimes peacefully, sometimes not).
Note: Talking about the Internet is like vocalizing about architecture. You can go on and on about its structure, history, and future, but it doesn't mean anything until you travel around and see it for yourself.