The Internet is a world wide computer network through which you can send a letter, chat to people electronically or search for information on almost any subject you care to think of. Quite simply it is a "network of computer networks". It originated in the 1960's in the USA where the US defence was conscious of having its computer network destroyed by blowing up the central computer. A network was designed around the principle of "unreliable computers" - if one was destroyed or failed the remaining computers could still function. Each computer in the network acknowledges the existence of all of the others.