How does the internet work?

When you load a web page or send a message, your data is broken into small chunks called packets. Each packet is labeled with addressing information and sent across a vast network of routers, servers, and cables — including undersea fiber-optic lines that carry most international traffic. Using a shared set of rules called TCP/IP, packets may take different routes and are reassembled in the correct order when they arrive. Domain names like example.com are translated into numerical IP addresses by the DNS system, a kind of internet phone book. This decentralized, packet-switched design makes the internet remarkably robust: if one path fails, data simply reroutes.