In the general sense, an internet (with a lowercase "i") is a computer network that connects several other networks. The art of connecting networks in this way is called internetworking. See also the related terms intranet and extranet. As a proper noun, the Internet is the world-wide, interconnected system of computers (plus the information and services they provide and their users) that uses the TCP/IP suite of protocols. Thus, the largest internet in the world is called simply "the" Internet.
During the 1990s, the Internet successfully accommodated the majority of previously existing computer networks.
This is often attributed to the lack of central administration, which allows organic growth of the network. The core networks forming the Internet started out in 1969 as the ARPANET devised by the United States Defence Advanced Research Projects Agency (ARPA). An important step in the development was the National Science Foundation's (NSF) building of a university backbone, the NSFnet, in 1986. Important alien networks that have successfully been accomodated within the Internet include Usenet, Fidonet, and Bitnet. See History of the Internet.
The Internet is held together by bi- or multilateral commercial contracts (e.g. peering agreements) and by technical specifications or protocols that describe how to exchange data over the network. These protocols are formed by discussion within the Internet Engineering Task Force (IETF) and its working groups, which are open to public participation and review. These committees produce documents that are known as Requests For Comments (RFCs). Some RFCs are raised to the status of Internet Standard by the Internet Architecture Board (IAB).
Some of the popular services on the Internet are E-mail, Usenet Newsgroups, FTP, the World Wide Web, Gopher, Telnet, WAIS, Finger, IRC, MUDs, and MUSHs. Some other popular services of the Internet were not created this way, but are based on proprietary systems. These include ICQ, AIM, CDDB.
The Internet has a large and growing number of users that have created a distinct culture. See Netiquette, Internet friendship, Internet romance, Trolls and trolling, Flaming, Cybering, Hacktivism, Internet humor, Internet slang, Internet in Art, PSTN.