HTML5 is the new standard for HTML that provides new semantic elements, canvas drawing, video/audio playback, and improved form controls. It is a collaboration between W3C and WHATWG to address changes to the web since 1999. Key new features include the <canvas> element for drawing, <video> and <audio> elements for media playback, and new form controls like date pickers. Browser support is still evolving but many features are already supported in modern browsers. HTML5 aims to standardize features and reduce reliance on plugins like Flash.