What is HTML5? Definition and explanations
HTML is the language that describes a web page's structure: headings, paragraphs, lists, links, images, forms. HTML5, its modern version maintained as a living standard by the WHATWG, adds semantic tags, native video and audio, canvas and local storage. It is the skeleton that CSS styles and JavaScript makes interactive.
In one sentence
HTML describes a web page's structure; HTML5 is its modern, semantic version.