In networking terms, an internet is simply the interconnection of two or more networks (it is a contraction of the words inter and network meaning literally a network of networks).

Literally a interconnection of networks, the Internet (capital I) is the global network of networks that provides the infrastructure for, among many other things, the World-Wide Web, email, and video on demand systems like BBC's iPlayer. In physical terms, the Internet is the collection of hosts, routers and links that allow heterogeneous networks to connect to each other and participate in the transfer of information from end-system (host) to end-system. In protocol terms IP is the network protocol that defines the encapsulation, addressing and routing scheme that is needed to transmit packets of data from host to router and router to router. For many applications, reliable data transfer over IP is provided by TCP and so the Internet is often said to be a TCP/IP network. However, strictly speaking, IP defines the Internet and is the protocol that all hosts and routers must implement to participate in the Internet.

The Internet is a Packet Switched Network in which long messages are broken up into small packets of data (called datagrams) that are addressed, transmitted and routed independently of each other (rather like letters in envelopes are moved by the Royal Mail) by the Packet Switches (routers) that act as sorting offices for the network. The networks themselves are interconnected by routers, and the Internet addressing scheme is based on a hierarchy of Internet Service Providers (ISPs). See also: IP, IP address and IP routing.

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