HTML

Every page on the internet is, at its core, a text file. This file contains not only the visible text, but also information about what role each part plays. HTML is the language used to mark these roles. For example, you write a marker around a line that means: this here is a heading. A browser, meaning the program used to display web pages, reads these markers and builds the finished page from them. The abbreviation stands for Hypertext Markup Language, roughly meaning: a language for marking up linked text.

Why half the internet runs on this one language

HTML is the shared foundation that everyone has agreed on. No matter whether you open a page with Chrome, Safari, or Firefox, on a phone or a laptop: the content arrives in the same language. Each program is free to decide exactly how it renders the result. Without this shared standard, every website would need its own version for every device.

A second point is linking. HTML has the concept of the link, a reference from one page to another. This is precisely what gave rise to a network of pages in the first place, rather than just a collection of separate documents. Search engines still use these links today to discover new pages.

Important for AI topics: language models were trained to a large extent on text from the web. This text existed as HTML and first had to be stripped of its markup. Even when an AI assistant looks something up on the web today, it first receives HTML and has to filter out the actual content from it. How cleanly a page is marked up therefore also determines how well a machine can understand it.

Tags, attributes, and the division of labor with CSS

The markers in HTML are called tags. They are written in angle brackets and usually come in pairs: one at the beginning, one at the end of the marked area. So a p tag means paragraph, and an h1 tag means the most important heading on a page. Whatever sits between the two tags belongs to that element.

Tags can carry additional information, so-called attributes. For a link, this holds the target address; for an image, the file name and an alternative text for people who have the page read aloud to them. Elements can also be nested within one another. This creates a tree structure: the page contains a text area, which contains paragraphs, which contain individual links.

A common misconception is that HTML is responsible for appearance. That is no longer true today. HTML only describes the meaning of the components. Colors, font sizes, and layout are the job of CSS, a separate language for design. For movement and interaction, JavaScript comes into play, an actual programming language. HTML itself is not a programming language, because it doesn’t compute anything and doesn’t make any decisions.

HTML in everyday life: page source, newsletters, and website builders

You can look at HTML at any time. In most browsers, there is a menu option called View Page Source. What appears then is exactly the file that the browser received from the server. On large sites this looks cluttered, because ads, tracking, and design take up a lot of space. But you can quickly recognize the basic building blocks.

You also encounter HTML outside of websites. Newsletters and many emails are written in HTML, as are the help pages in many apps. When an email looks strangely broken, it is often because a mail program renders certain markup differently.

Most people never type HTML themselves. Website builder systems like Wordpress or Shopify generate it in the background, and AI tools now also write entire pages on request. Even so, it’s worth knowing the basics. Anyone who understands how a page is structured can find errors, mark up content accessibly, and figure out why a machine read a page incorrectly.