How the Internet Works Quiz
A network of networks
The internet isn't one giant computer or one company. It's thousands of separate networks, run by different companies, universities and governments, all connected and all following the same shared rules, called protocols.
It grew out of ARPANET, a US research network that sent its first message in 1969. The plan was to type LOGIN, but the system crashed after two letters, so the first message was 'LO'. On January 1, 1983, ARPANET switched to the TCP/IP protocols that the internet still uses.
The World Wide Web, the pages and links you browse, came later, in 1989. It's just one of the services that run on the internet, alongside email, video calls and online games.
Packets and addresses
When you send a photo or load a page, the data is chopped into small pieces called packets. Each packet carries the address of where it's going.
Every device online has an IP address, a number that works like a postal address. Routers along the way read each packet's address and pass it on, step by step, toward its destination. Packets from the same file can take different routes and are put back together at the end.
People find addresses like numbers hard to remember, so the Domain Name System, or DNS, works like a phone book, turning names like example.com into the numbers computers use.
The physical internet
The internet is very physical. Almost all data traveling between continents goes through cables laid on the sea floor, hundreds of them, some longer than 20,000 km.
Most of those cables use optical fiber: thin strands of glass that carry data as flashes of light, very fast, over long distances.
Websites and apps live on computers in huge buildings called data centers. At home, Wi-Fi uses radio waves to link your phone or laptop to a router, which connects to the wider network by cable. In remote places, satellites can fill the gap.