Computers on the internet follow shared sets of rules called protocols. TCP is a set of rules that makes sure packets arrive complete and in order. TCP and IP are used together so often that the pair is called TCP/IP.

The ARPANET, the internet's direct forerunner, began with four computers in late 1969. In the 1970s, scientists Vint Cerf and Bob Kahn designed TCP. The same two men invented IP in 1974. In January 1983 the ARPANET standardized on the TCP/IP protocols. They had been planned as the switch from the older NCP.

A packet moves from machine to machine. Each machine looks at the destination address and passes the packet along. A router decides where to send packets next.

To open a website, a browser first uses DNS to find the server's address. If a DNS server does not know a website's address, it can ask another DNS server. Root servers know where to look.

HTTPS is a secure version of HTTP. It uses TLS to scramble what a browser and a server send each other.

Tim Berners-Lee invented the World Wide Web in 1989. He was working at CERN. By Christmas 1990, he had defined HTML, HTTP and URLs. He had also written the first browser and server software.

The first web server in the United States came online in December 1991. It was at a physics laboratory in California. On 30 April 1993, CERN made the web software free for anyone to use. Mosaic, a browser released in 1993, could show pictures and text together on web pages.

The web and the internet are not the same. The internet is the network, and the web is one service that runs on it. Email is another service built on top of the internet, besides the web.

As of November 2026, almost all the data that travels between countries goes through cables laid on the sea floor. Satellites are useful for reaching places that fiber cables do not yet reach. But cables carry far more data at a much lower cost.

As of November 2026, most damage to undersea cables comes from human activity. Fishing and ships dragging anchors are examples. It does not come from sharks. Companies spread their traffic across several cables. If one breaks, the network keeps running over the others while the broken one is repaired.

Words to know

• protocols: shared rules
• router: sends packets onward
• forerunner: earlier version
• scramble: mix up