World Wide Web (WWW)
The World Wide Web is a huge collection of web pages linked to each other by hyperlinks, stored on computers all over the Internet. It was invented by Tim Berners-Lee in 1989–91 at CERN.
The Internet is the network (roads and wires); the Web is one service that runs on it (like shops along the roads). Email and VoIP are other services on the same Internet.
The Web rests on three ideas: HTML (the page language), URL (the address of each page) and HTTP (the rules for asking and sending pages).
HTML and XML
HTML (HyperText Markup Language) describes how a page should be displayed. It uses a fixed set of tags in angle brackets, like <h1>, <p>, <img>, <a href="…">.
<html>
<body>
<h1>My School</h1>
<p>Welcome!</p>
</body>
</html>XML (eXtensible Markup Language) is used to store and carry data. You make your own tags, and every tag must be closed.
<student> <roll>7</roll> <name>Asha</name> </student>
| HTML | XML |
|---|---|
| Displays data | Stores and carries data |
| Tags are fixed (predefined) | You define your own tags |
| Not case-sensitive; some tags need no closing | Case-sensitive; every tag must close |
| Mistakes are often ignored by browsers | Must be well-formed or it fails |
Domain names and DNS
IP addresses are hard to remember, so websites get a domain name, a readable name like ncert.nic.in or wikipedia.org.
- The last part is the top-level domain (TLD). Generic:
.com(commercial),.org(organisations),.edu(education),.gov(government),.net(network). Country code:.in(India),.jp(Japan),.uk. - Parts to the left are sub-domains: in
www.cbse.gov.in,inis the TLD,gova second level,cbsethe organisation andwwwthe web server.
The Domain Name System (DNS) is a worldwide set of servers that turns a domain name into an IP address, like a phone book turns a name into a number. This is called name resolution.
URL: Uniform Resource Locator
A URL is the complete address of one resource (page, image, file) on the Web.
https://www.example.org/class12/notes.html
https://— protocol (how to fetch it)www.example.org— domain name (which server)/class12/notes.html— path (folder and file on that server)
An absolute URL has all parts. A relative URL such as notes.html or ../images/logo.png is used inside a site and is understood from the current page's location.
A domain name is only one part of a URL.
Website, web page, web browser, web server
- Web page: one document on the Web, usually an HTML file, with text, images and links.
- Website: a set of related web pages under one domain, linked together and starting at a home page. Static sites show the same content to everyone; dynamic sites build pages on the fly (like your bank account page).
- Web browser: software that requests web pages and displays them: Chrome, Firefox, Edge, Safari. It reads HTML, shows images, runs scripts, keeps history, bookmarks and cookies. Add-ons/plug-ins add extra features.
- Web server: a computer (and software such as Apache or Nginx) that stores website files and sends them when a browser asks, using HTTP/HTTPS. It is switched on all the time and has a fixed IP address.
Web hosting
Web hosting is a service that stores your website's files on a web server connected to the Internet 24×7, so anyone can open it. You pay a hosting provider for space, speed and security.
Steps to put a website online:
- Make the pages (HTML, images, etc.).
- Buy (register) a domain name from a registrar.
- Buy hosting space on a web server.
- Upload the files (often with FTP).
- Point the domain name to the server's IP address in DNS.
Types include shared hosting (many sites on one server, cheap), dedicated hosting (a whole server for one site) and cloud hosting (spread over many servers).
Try it: take a URL apart
Open any three websites you use. For each, copy the URL from the address bar and split it into protocol, domain name and path. Name the TLD and say whether it is generic or a country code. Then right-click a page and choose "View page source": you are looking at the HTML the web server sent. Use the free-play step in the 3D to build a URL and watch its trip.
Key formulas and definitions
- URL = protocol :// domain name / path
- DNS: domain name → IP address
- HTML shows data (fixed tags) · XML stores/carries data (own tags)
- Browser asks (client) → Web server answers · Hosting = renting server space
Worked examples
1. Split https://www.cbse.gov.in/results/index.html into its parts.
Protocol: https. Domain name: www.cbse.gov.in (TLD .in). Path: /results/index.html (folder results, file index.html).
2. Which is generic and which is country-code: .org, .in, .edu, .jp, .gov?
Generic: .org, .edu, .gov. Country code: .in (India), .jp (Japan).
3. Write XML for a book with title 'Python Basics' and price 350.
<book> <title>Python Basics</title> <price>350</price> </book> — the tags are made up by us, and every tag is closed.
4. Put in order what happens when you open a website: server sends HTML, browser shows page, DNS finds IP, you type URL, browser sends HTTP request.
Type URL → DNS finds IP → browser sends HTTP request → server sends HTML → browser shows page.
5. A student made a website on her laptop. Why can't her friends open it, and what does she need?
Her laptop is not a server that is always online with a fixed public address. She needs web hosting (space on a web server) and a domain name that points to it.
6. Is 'google.com' a URL or a domain name?
It is a domain name. A full URL also has the protocol (and maybe a path), like https://google.com/maps.
Common mistakes
- Saying the Internet and the WWW are the same; the Web is one service on the Internet.
- Calling a domain name a URL; the domain is only one part of the URL.
- Thinking XML replaces HTML; XML carries data, HTML shows it.
- Mixing web browser (client software) and web server (computer that stores and sends pages).