1. With a lower-case "i", any set of networks interconnected with routers.
2. With an upper-case "I", the world's collection of interconnected networks. The Internet is a three-level hierarchy composed of backbone networks, mid-level networks, and stub networks. These include commercial (.com or .co), university (.ac or .edu) and other research networks (.org, .net) and military (.mil) networks and span many different physical networks around the world with various protocols, chiefly the Internet Protocol.
Until the advent of the web in 1990, the Internet was almost entirely unknown outside universities and corporate research departments and was accessed mostly via command line interfaces such as telnet and FTP. Since then it has grown to become a ubiquitous aspect of modern information systems, becoming highly commercial and a widely accepted medium for all sort of customer relations such as advertising, brand building and online sales and services. Its original spirit of cooperation and freedom have, to a great extent, survived this explosive transformation with the result that the vast majority of information available on the Internet is free of charge.
While the web (primarily in the form of HTML and HTTP) is the best known aspect of the Internet, there are many other protocols in use, supporting applications such as electronic mail, chat, remote login and file transfer.
There were 20,242 unique commercial domains registered with InterNIC in September 1994, 10% more than in August 1994. In 1996 there were over 100 Internet access providers in the US and a few in the UK (e.g. the BBC Networking Club, Demon, PIPEX).
There are several bodies associated with the running of the Internet, including the Internet Architecture Board, the Internet Assigned Numbers Authority, the Internet Engineering and Planning Group, Internet Engineering Steering Group, and the Internet Society.
The Internet Index - statistics about the Internet.