How the Internet Works

The internet is a worldwide network that lets one computer send data to another, and the World Wide Web is one of the things built on top of it — the collection of pages and sites you open in a browser — so the web runs on the internet the way programs, as the earlier topics described, run on a computer. A network is simply two or more computers connected so they can exchange data; the internet is the enormous network-of-networks that links billions of devices worldwide, and the key idea that makes it work is that any message is broken into small chunks called packets, each sent separately and reassembled at the destination, so a single wire or connection can carry pieces of many different conversations at once instead of being tied up by one. For packets to find their way, every device on the internet has an IP address, a numeric label much like a postal address, and because those numbers are hard for people to remember, the Domain Name System (DNS) acts as the internet's phone book: when you type a name like `example.com`, DNS looks up the IP address the name points to so your computer knows where to send its packets. A protocol is an agreed set of rules two computers follow so they understand each other, and the web's protocol is HTTP (HyperText Transfer Protocol): your browser is a client that sends an HTTP request — essentially "please send me this page" — to a server, a computer whose job is to store pages and wait for such requests, and the server replies with an HTTP response containing the page's content. That content is usually HTML, the language that describes a page's text, headings, links, and images, which the browser reads and renders into the page you actually see — HTML is to a web page what the source code from the how-programs-run topic is to a program: human-written text that a program turns into something usable. When the connection is secured with HTTPS, the same exchange happens but the packets are encrypted so that anyone who intercepts them in transit sees only scrambled data, which is why the lock icon matters whenever you log in or enter payment details. Putting it together, visiting a site is a quick round trip built from all these pieces: DNS turns the name into an IP address, your request is split into packets and routed across many networks to the server, the server sends the page back the same way, and your browser reassembles and renders it — the same underlying machinery whether the server is next door or on another continent.

You type example.com
a human-friendly name, not an address the network can route to
DNS lookup
the internet's phone book turns the name into an IP address
Request split into packets
routed across many networks to the server at that IP address
Server sends the page back
an HTTP response carrying HTML, reassembled and rendered by your browser
One Web Request, End to End client asks, DNS translates, server answers Browser the client DNS name -> IP address Server stores the page 1. look up example.com 2. here is the IP address 3. HTTP request, split into packets 4. HTTP response: the page's HTML the browser reassembles the packets and renders the HTML into the page you see with HTTPS, every packet in steps 3 and 4 is encrypted in transit
Why Messages Travel as Packets one message is split up, sent separately, and reassembled at the far end Whole message e.g. an image or a page pkt 1 pkt 2 pkt 3 pkt 4 each packet can take its own route across the network reassembled in order at the destination missing packets are simply re-sent packets let one connection carry pieces of many conversations at the same time

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