The Internet is a global network of interconnected networks. It supports services such as the World Wide Web, e-mail, online banking, search engines and social media.

Important historical exam points include ARPANET, the later development of the World Wide Web, ICANN, and Tim Berners-Lee's contribution to the web. The supplied material notes ARPANET in the 1970s, MILNET in 1984, WWW in 1989 and ICANN in 1998.

• Internet: public/global network.
• Intranet: private organisational network.
• Extranet: controlled organisational network access extended to authorised outsiders such as partners.

A connection involves a device/network interface, an Internet Service Provider and suitable software such as a browser or e-mail client. Older and modern access methods include dial-up, wired broadband, mobile networks, Wi-Fi and fibre connections.

Exam conversion: 1 byte = 8 bits. Data-rate prefixes are commonly tested: kbps, Mbps and Gbps.

The World Wide Web is a system of interlinked hypertext documents accessed over the Internet. A URL (Uniform Resource Locator) identifies the location/address of a resource. A web browser retrieves and renders web content, interpreting HTML and displaying text, images, video and scripts.

A simplified sequence is: enter URL → DNS lookup → request page → server response → browser displays page. DNS translates a domain name into an IP address so the device can locate the appropriate server.

Search engines use crawlers/spiders to discover pages, build indexes and return results from their index. The key distinction is: crawler collects, index stores, search retrieves.

An e-mail address follows the pattern username@domain. SMTP is associated with sending e-mail; POP/IMAP are used for retrieving/accessing mail. In the message header, To is for primary recipients, Cc shows secondary recipients to other recipients, and Bcc hides recipients from one another.

DNS resolves domain names to IP addresses. Static pages generally deliver predetermined content; dynamic pages can generate content in response to requests, data and user interaction.

HTML means HyperText Markup Language. It is a markup language, not a programming language. HTML structures web content; CSS is primarily for presentation/style and JavaScript adds client-side interactivity.

High-frequency tags: <html>, <head>, <title>, <body>, <h1>-<h6>, <p>, <br>, <a>, <img>, <table>, <ul>, <ol>, <form>.

<ul> creates an unordered list; <ol> creates an ordered list. <a href> creates a hyperlink. <img src> embeds an image, while alt supplies alternative text when an image cannot be displayed.

• Internet ≠ WWW. WWW is a service that runs over the Internet.
• Browser ≠ search engine. Browser displays/retrieves web pages; search engine helps locate indexed information.
• URL ≠ IP address. URL is a resource locator; DNS can resolve a domain name to an IP address.
• HTML ≠ programming language.
• SMTP is for sending e-mail; POP/IMAP are associated with retrieval.