Internet applications and websites

The essentials

The Internet supports many applications: the World Wide Web, email, chat, video calls and Voice over IP. Websites are stored on web servers and reached through their URLs.

Key points

• URL (Uniform Resource Locator): the address of a resource on the web. In https://www.example.com/books/index.html, "https" is the protocol, "www.example.com" is the domain name, and "/books/index.html" is the path to the file.
• WWW: a system of interlinked hypertext documents (web pages) written in HTML and accessed using HTTP.
• Email: sending messages over the Internet. An email address has the form username@domainname. Messages can carry attachments; CC sends copies to others and BCC sends copies without showing those addresses to other recipients.
• Chat: real-time exchange of text messages; video chat adds audio and video.
• VoIP (Voice over Internet Protocol): sends voice calls as data packets over the Internet. It is cheaper for long distances but depends on network quality.
• Website: a collection of related web pages under one domain; the first page is the home page.
• Static web page: content is fixed and the same for every visitor; changed only by editing the file. Written mainly in HTML.
• Dynamic web page: content is generated when the page is requested and can change by user, time or data, for example a page showing a student's own result. Uses server-side or client-side scripts such as PHP, JavaScript, Python or ASP.
• Web server: a computer and software that stores websites and sends web pages to clients (browsers) on request.
• Web hosting: a service that stores a website on a server connected to the Internet so that people can access it, usually after registering a domain name.

Common mistakes

• Thinking a website with images is dynamic. Dynamic means generated on request, not decorated.
• Mixing the domain name with the full URL.