How the Internet Actually Works

Imagine you want to send a 1,000-page book to a friend on the other side of the world — instantly. You can't send it as one enormous bundle. Instead, you tear it into individual pages, post each page separately by different routes, and trust your friend to reassemble them in order. Somehow, every page arrives in seconds. That is almost exactly what your device does every time you load a website or send a message. How do billions of devices worldwide manage to talk to each other without constant chaos?

A network is any group of two or more devices connected so they can share data. Your school Wi-Fi is a network. Your home router creates a network. The internet is the global system that connects millions of these smaller networks together — it is, quite literally, a network of networks. Every device on the internet needs a unique address so data can find it. This is called an IP address (Internet Protocol address). Think of it like a postal address for your device. A typical IPv4 address looks like four numbers separated by dots, for example 192.168.1.1. Because there are now more devices than IPv4 can handle, a newer system called IPv6 uses longer addresses to give every device its own unique number. When you request a webpage or send a file, your device does not send the data as one solid block. Instead it is split into small chunks called packets. Each packet contains a piece of the data plus header information — the sender's IP address, the destination IP address, and a sequence number so the packets can be put back in order. Packets from the same message may travel by completely different routes across the internet, choosing the fastest available path at that moment. Devices called routers direct packets along these routes. Each router reads the destination IP address on a packet and decides the best next step to send it, like a series of post offices passing a letter towards its destination. For all of this to work, every device must follow the same set of rules, called protocols. The most important pair of protocols is TCP/IP — Transmission Control Protocol and Internet Protocol. IP handles addressing and routing. TCP makes sure all packets arrive and are reassembled in the correct order. If any packet is missing, TCP requests it again. This is why your downloads are accurate rather than scrambled. For web browsing specifically, another protocol called HTTP (or its secure version HTTPS) tells your browser and the web server how to ask for and send webpage data. The 'S' in HTTPS stands for Secure — it means the data is encrypted, scrambled so that only the sender and receiver can read it.