What is the Internet?

A network is two or more devices connected so that they can exchange data. Your phone, a smart TV, a game console and the computers that hold your favourite website are all just machines sending messages to each other.

Networks come in sizes:

• A LAN (local area network) covers a small place such as a home, a school or an office. It usually hangs off one router or switch.
• A WAN (wide area network) joins networks across cities, countries and oceans.

Most conversations on a network have two roles. A client asks for something (your browser asking for a page) and a server answers (the machine that stores and sends the page). One device can play both roles: your laptop is a client when it browses and a server when it shares a file with a friend's laptop.

The Internet is a network of networks. It is not one big machine owned by one company. It is millions of separate networks (homes, schools, companies, universities, phone operators, governments) that agree to pass each other's data along, using the same set of rules. Those shared rules are called protocols. The two most important ones give the family its name: TCP/IP.

Because it is a joining-together of many networks, no single organisation runs the Internet. Each network is run by whoever owns it. Some groups agree on the shared rules: engineers write open standards, and organisations hand out the unique addresses and names so that no two devices clash. But nobody can switch the whole thing off or control all of it.

The Internet is not the Web. This is the most common mix-up.

• The Internet is the global network that carries the data.
• The World Wide Web is one service that runs on the Internet: pages linked together, fetched with a protocol called HTTP and shown in a browser.

E-mail, online games, video calls, music streaming and software updates all use the Internet, and most of them are not the Web. The Web was proposed by Tim Berners-Lee at the research centre CERN in 1989, and the first website went online in 1991.

The Internet itself is older. The experimental network ARPANET sent its first message in 1969 between two university computers in California, and the network switched over to the TCP/IP rules on 1 January 1983, a date often called the birthday of the Internet.