The Internet and The World Wide Web (WWW)

The two are easy to confuse because most people only experience the internet through web pages.

The internet is the global INFRASTRUCTURE — a network of networks. It's the wires, cables, routers, undersea cables, satellites, Wi-Fi access points and the protocols that route packets between them.

The World Wide Web is ONE SERVICE running on the internet — a collection of HTML pages and other resources accessed via URLs using HTTP/HTTPS, displayed by web browsers.

The internet ALSO carries:

• Email (SMTP, IMAP, POP3)
• File transfer (FTP, SFTP)
• Voice and video calls (VoIP, WebRTC)
• Online gaming
• Streaming media
• Cloud storage and backups
• IoT device telemetry

Cambridge tip. Mark scheme separates the two: internet = INFRASTRUCTURE; web = a SERVICE that uses the infrastructure. Saying 'they are the same' is an immediate mark loss.

A URL (Uniform Resource Locator) is the address of a resource on the web. Take https://www.tutopiya.com/learning-portal/login?ref=email#form and break it down:

• https:// — the protocol. Tells the browser how to communicate (and that the connection is encrypted).
• www.tutopiya.com — the domain. The human-readable name of the server. www is a subdomain; tutopiya is the registered domain; .com is the TLD.
• /learning-portal/login — the path. The specific resource on that server.
• ?ref=email — the query string (optional). Key-value parameters used by the server.
• #form — the fragment (optional). A specific anchor within the page.

Cambridge tip. Mark scheme typically asks for the THREE main parts: protocol, domain, path. Query and fragment are bonus knowledge.

HTTP (HyperText Transfer Protocol) is the protocol web browsers and servers speak. The browser sends a REQUEST (e.g. GET /login) and the server returns a RESPONSE (HTML, status code, headers).

HTTPS = HTTP over TLS. Same HTTP requests/responses, but encrypted using TLS (Transport Layer Security). The TLS handshake at the start of the connection:

1. Client and server exchange certificates (asymmetric crypto verifies the server's identity).
2. They negotiate a SHARED SYMMETRIC SESSION KEY using asymmetric crypto.
3. The actual HTTP traffic is encrypted with that symmetric key for speed.

This combines the strengths of both encryption families (asymmetric for distribution, symmetric for bulk speed) — the same hybrid pattern from Topic 3.

Why HTTPS matters. Without it, anyone on the same network (e.g. a public Wi-Fi) can read your traffic in plaintext. HTTPS protects:

• Login credentials.
• Payment details.
• Personal messages.
• Cookies and session tokens.

Cambridge tip. Top-band candidates explain HTTPS as 'HTTP + TLS' rather than treating it as a separate protocol — and reference the asymmetric/symmetric hybrid handshake.

From the moment you press Enter to seeing a page on screen, the browser does a lot of work:

1. Parse the URL. Split into protocol, domain and path.

2. DNS lookup. Ask the DNS resolver to translate the domain to an IP address. The resolver may return a cached answer or walk the DNS hierarchy (root → TLD → authoritative server).

3. TCP connection. Open a TCP connection to the IP, on port 443 (HTTPS) or 80 (HTTP).

4. TLS handshake (HTTPS only). Negotiate certificates and a session key.

5. HTTP request. Send a GET (or POST) request for the path.

6. Server response. The web server returns an HTTP response with the requested HTML, plus a status code (200 OK, 404 Not Found, 500 Server Error).

7. Browser parses HTML. Builds a document tree of the page.

8. Linked resources. The browser requests CSS, JavaScript files, images, fonts as it discovers them in the HTML.

9. Render. The browser paints the page, runs JavaScript, fires events.

All this typically completes in well under a second.

Cambridge tip. When asked, examiners want at least: URL parsed → DNS → connection → HTTP request → response → render. Naming DNS specifically is usually worth a mark on its own.

ISP (Internet Service Provider). The company that physically connects your home/school/office to the internet — typically over fibre, cable, DSL or 5G. They run the modem-side equipment and route your traffic toward its destination.

DNS (Domain Name System). A hierarchical, distributed system of servers that maps human-readable domain names to IP addresses.

• ROOT servers — top of the hierarchy (only ~13 logical clusters globally).
• TLD servers — handle each .com, .org, .uk, etc.
• AUTHORITATIVE servers — the specific server with the records for one domain.
• RESOLVER (run by your ISP or a public service like 1.1.1.1) — does the lookup on your behalf.

Web browser. The application that turns HTTP responses into rendered pages. Modern browsers also:

• Run JavaScript and store cookies.
• Block trackers (depending on settings).
• Manage saved passwords.
• Verify HTTPS certificates.
• Cache resources locally for speed.

Cambridge tip. When questions name 'how a website loads', mention all three: ISP for connectivity, DNS for name lookup, browser for rendering.