HTML5 is the new standard for web development that provides new semantic elements, audio/video playback, canvas drawing, and geolocation. It is being developed jointly by the W3C and WHATWG standards bodies. Some key features include new semantic elements like <header>, <footer>, <nav>, improved forms with new input types like date, time and color, and multimedia elements <video> and <audio> for embedding video and audio. Browser support is still evolving but major browsers support many HTML5 features. The document provides details on HTML5 features, elements, attributes and how it improves upon previous HTML standards.