The Internet & the World Wide Web

Quick Summary

• The Internet is a global network of networks (a WAN) — the infrastructure. The World Wide Web is a service that runs on it — websites and pages.
• HTTP sends data between browser and server in plain text; HTTPS does the same thing but encrypts it, which is why it's used for passwords and payments.
• A web browser is software that requests, receives, and renders (displays) web pages — plus it gives you tabs, bookmarks, history, and an address bar.
• A web server is a remote computer that stores a website's files and hands them out on request, 24/7, to many users at once.
• A URL is the text address of a page, made of three parts: protocol → domain name → file path.
• The DNS is the internet's phone book — it turns a human-friendly domain name into the numeric IP address computers actually need.
• HTML is the language that structures and presents a web page's content, built from opening/closing "tags".
• Cookies are tiny files that remember things about you. Session cookies live in RAM and vanish when you close the browser; persistent cookies live on the hard drive and survive between visits.

1. The Internet vs the World Wide Web

This is the single most commonly mixed-up idea in this whole topic, and examiners know it — so let's nail it properly, not just memorise a sentence.

What is the Internet?

• The Internet is a global network of networks — millions of smaller networks (home networks, school networks, company networks) all linked together.
• It is the most well-known example of a Wide Area Network (WAN) — a network that spans a huge geographical area, in this case the entire planet.
• Its job is to be the infrastructure — the cables, satellites, routers, and connections — that makes it possible for data to travel from one device to another anywhere in the world.

What is the World Wide Web?

• The Web (or "the web") is a collection of websites and web pages that you access using the Internet.
• It was invented in 1989 by Tim Berners-Lee, who wanted a way for people to share and access information globally.
• It's made of interconnected documents and multimedia files (text, images, video) stored on web servers all around the world, and linked together by hyperlinks.
• You access web pages through a web browser, which talks to web servers to fetch and display that content.