HTML is a language used to describe text on web pages. It uses tags to format and lay out text, images, and other content. Some key tags include <HTML> and </HTML> to define an HTML document, <HEAD> and </HEAD> for metadata, and <BODY> and </BODY> to contain the visible page content. The document is saved with a .html or .htm file extension. HTML allows adding formatting, hyperlinks, tables, images and other enhancements to make the page more informative and visually appealing. Proper encoding must be specified so non-Latin characters display correctly across different browsers and platforms.