A web browser is a program that gets web pages and shows them to you. A web page is built from files. Some are code written in HTML, CSS and JavaScript. Emails, web pages, songs and videos all travel across the internet as packets.

When you use a phone, the signal travels through the air only as far as the nearest cell tower. From there the data goes through cables on land and under the sea.

The router in a home is often one box that works as a switch, a router and a modem together. A network switch is a small computer that forwards messages toward the right recipient inside one local network.

A computer's IP address is usually given to it by its internet service provider, or ISP.

An ISP manages special routers. They are linked together and can also reach other ISPs' routers, so a message is carried through a network of networks. Networks join the internet by following two shared rules. They chop messages into packets in the Internet Protocol format. They also use the same address system to send each packet toward its destination.

IP is a "best efforts" service. It tries to deliver packets but cannot promise they all arrive or arrive in order. The packets of one message can travel along different paths to the same place.

On October 29, 1969, a computer at UCLA made the first connection to a computer at the Stanford Research Institute. The first log-in attempt crashed the far computer. The next try worked.

The National Science Foundation launched NSFNET in 1986. It grew from about 2,000 connected computers in 1986 to more than 2 million by 1993. By late 1993 there were over 500 known web servers, and the web carried about 1% of internet traffic. By the end of 1994, the web had 10,000 servers and 10 million users.

A few technical things, such as domain names and IP addresses, must mean the same everywhere. One group coordinates them: ICANN. ICANN was formed in 1998. It does not control what is on the internet and cannot stop spam. DNS is a decentralized system: no single list holds every name.

Modern undersea cables use light: lasers send flashes down thin glass fibers to the other end. Most of the way across an ocean, a cable is about as wide as a garden hose. The glass fibers inside are about as thin as a human hair.

As of November 2026, cable breaks are common: roughly 200 faults happen each year, according to the International Cable Protection Committee. Countries need more than one cable so that connections keep working if one is damaged.

Words to know

• browser: page-getting program
• ICANN: names coordinator
• switch: forwards messages locally
• packets: small pieces