HTML5 is the latest revision of the HTML standard. It is a language for structuring and presenting content for the World Wide Web, a core technology of the Internet.
WHATWG (Web Hypertext Application Technology Working Group) a new group of W3C members felt that W3C is not paying enough attention to the real-world development needs of language, it has started working on a new specification of HTML-HTML5. Hence HTML5 is a new version of HTML 4.01 and XHTML 1.0 focusing on the needs of Web application developers as well as addressing issues found in the current specifications.
In particular, HTML5 adds many new syntactical features. New elements, such as <section>, <article>, <header>, and <nav>, are the basic parts of semantic content of documents. These also include the <video>, <audio>, and <canvas> elements, as well as the integration of SVG content. These features are designed to make it easy to include and handle multimedia and graphical content on the web without having to resort to proprietary plugins and APIs. While some elements and attributes have been removed. Some elements, such as <a>, <cite> and <menu> have been changed, redefined or standardised. The APIs and DOM are no longer re-considerations, but are fundamental parts of the HTML5 specification.
HTML5 also defines in some detail the required processing for invalid documents, so that syntax errors will be treated uniformly by all conforming browsers and other user agents.