Difference between Internet, Intranet & Extranet

Internet
1) Definition of internet
The Internet, sometimes called simply "the Net," is a worldwide system of computer networks - a network of networks in which users at any one computer can, if they have permission, get information from any other computer (and sometimes talk directly to users at other computers). 2) When & by who was it started?

It was conceived by the Advanced Research Projects Agency (ARPA) of the U.S. government in 1969 and was first known as the Arpanet. 3) What was its purpose?
The original aim was to create a network that would allow users of a research computer at one university to be able to "talk to" research computers at other universities. A side benefit of Arpanet’s design was that, because messages could be routed or rerouted in more than one direction, the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster. 4) W...

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