Hypertext Markup Language, or HTML, is a programming language used to describe the structure of information on a web page. Together, HTML, CSS, and JavaScript make up the essential building blocks of websites, with CSS controlling a page's appearance, and JavaScript programming its functionality. You can think of HTML as providing the bones of a web page, while CSS provides the skin, and JavaScript provides the brains.

A web page can contain headings, paragraphs, images, videos, and many other types of data. Front-end developers use HTML elements to specify what kind of information each item on a web page contains — for instance, the "p" element indicates a paragraph. Developers also write HTML code to specify how different items relate to one another in the overall structure of the page.