"HTML" is an acronym that stands for hyper text markup language. "Hyper text" refers to links that connect Web pages and websites, and "markup language" means a set of markup tags.
The Mozilla Developer Network describes HTML as a language that "describes the structure and the semantic content of a Web document." Content for a webpage is sectioned off with HTML elements. An HTML document is defined with an opening HTML tag at the beginning of the code and a closing HTML tag at the end. These HTML tags tell a Web browser that it is an HTML document. Extensible hyper text markup language, or XHTML, is a stricter, more structured variation of HTML.