HTML HyperText Markup Language
The structure of a web page — what's a heading, a paragraph, a link or an image.
HTML is a markup language, not a programming language: you describe what things are, not what they should do. <h1>Title</h1> says "this is a title". CSS handles the look, JavaScript handles the behaviour.
HTML5 (2014) is today's version. Brought semantic elements (<article>, <nav>), built-in video without plug-ins, and a heap of form types.