HTML (HyperText Markup Language) is the standard markup language for creating web pages and web applications, serving as the foundation of all content on the World Wide Web. Developed by Tim Berners-Lee in the early 1990s, HTML structures documents through elements (tags) that define everything from headings and paragraphs to forms and multimedia. While HTML provides the skeleton of web content, it works alongside CSS for presentation and JavaScript for behavior. Understanding HTML's semantic elements, attributes, and best practices is crucial: properly structured HTML improves accessibility (screen readers can navigate content meaningfully), SEO (search engines index semantic markup more effectively), and maintainability.