The World Wide Web

⏱ 8 min✏️ Quiz at the end

The Web Is Not the Internet

People say "the internet" when they mean "the web", but they are different things — and the difference is worth understanding.

  • The internet is the network of networks: cables, routers, packets, addresses. It moves data. It does not care what the data is.
  • The World Wide Web is one service running on top of it: billions of pages, connected by links, viewed in a browser.

Email, video calls, and online games also run on the internet but are not the web. The web is simply the most famous tenant of the building. It was invented in 1989 by Tim Berners-Lee, who proposed connecting documents with clickable links — hypertext — and gave the system away for free.

Clients and Servers

The web runs on a simple division of labour:

  • A web server is a computer that stores a website and waits, day and night, for requests. When one arrives, it responds with the requested page. Every website you have ever visited lives on servers, mostly in vast data centres.
  • A client is the device asking — your phone or laptop, running a browser (Chrome, Safari, Firefox, Edge). The browser sends requests, receives the response, and renders it into the page you actually see.

One server can answer thousands of clients at once. This request–response pattern is one of computing's great patterns — you will find it far beyond the web.

What a URL Means

Every page has an address — a URL. Take it apart:

https://www.example.com/lessons/binary
 └─┬─┘  └──────┬──────┘ └─────┬──────┘
scheme     domain name       path
(how)     (which server)  (which page)
  • Scheme — how to talk. https means the conversation is encrypted: anyone eavesdropping on the network sees scrambled data. The padlock in your browser means exactly this — insist on it whenever passwords or payments are involved.
  • Domain name — which site, in human-friendly words.
  • Path — which page on that site.

But packets need numeric IP addresses, not names. Enter DNS (Domain Name System) — the internet's phone book. Before anything else, your browser asks DNS: "what number is www.example.com?" and gets back something like 93.184.216.34.

What Actually Happens When You Visit a Page

The complete sequence, start to finish:

  1. You type a URL or click a link
  2. DNS lookup — the domain name becomes an IP address
  3. Request — your browser sends "please send me /lessons/binary" to that server
  4. The request crosses the internet as packets, router by router
  5. Response — the server sends back the page: HTML (the page's structure and text), plus images, styles, and scripts
  6. Rendering — your browser reads the HTML and draws the page

That last step surprises people: the server sends only code and data. The picture on your screen is assembled by your own device. HTML (HyperText Markup Language) describes what the page contains — "this is a heading", "this is a paragraph", "this links to that page" — and the browser decides exactly how to display it.

All of it — lookup, request, response, render — typically fits in under a second, and it happened right now, for this very page.

One page is a document; the web comes from links. Each link points at another URL, which points at another, spanning the whole world. Search engines exist to navigate this web: their software follows links from page to page, building an index of what exists — a searching problem at planetary scale.

Worked Example — Tracing a Single Click

Follow one concrete click all the way through, tying every idea in this lesson into one sequence: you are reading a news article and click a link reading "read our full report".

  1. The link's URL is https://reports.example.com/full-report — scheme https (encrypted), domain reports.example.com, path /full-report
  2. Your browser (the client) asks DNS: "what IP address is reports.example.com?" and receives an answer like 203.0.113.42
  3. Your browser sends a request to that address, across the internet as packets, asking specifically for /full-report
  4. The web server at that address receives the request, finds the matching page, and sends back HTML plus any images and styling
  5. Your browser renders the HTML — turning tags like "this is a heading" and "this is a paragraph" into the formatted page you actually read
  6. The page itself contains more links, ready to repeat this entire process the instant you click one of them

Every visible webpage you have ever loaded followed exactly this six-step journey — the only thing that changes between one click and the next is which server answers and what HTML comes back.

Why Some Pages Change Every Time You Visit

Not every page shown by a server is a fixed file sitting waiting to be sent. Many pages — a social media feed, a weather site, a search results page — are generated freshly by the server at the moment of your request: the server runs a program, often consulting a database, and builds a custom page just for that request (today's weather, your specific search terms, posts from accounts you follow). This is why the "process" step in the input-process-output model is doing real, sometimes heavy work on the server's side — not merely retrieving an unchanging file — even though from your browser's point of view, the six-step journey above looks identical either way.

Key Words

  • World Wide Web — the linked pages and sites that run as a service on the internet
  • Web server — a computer that stores websites and responds to page requests
  • Browser — the client program that requests pages and renders them for you
  • URL — the address of a page: scheme, domain name, path
  • DNS — the system translating domain names into IP addresses
  • HTML — the language describing a page's structure and content
  • HTTPS — the secure, encrypted version of the web's request protocol
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