HTML 5 is the latest version of the HTML standard. It includes several new elements and features to improve structure and behavior. Some key changes include new semantic elements like <article>, <aside>, <header>, and <footer>; built-in support for audio and video; the <canvas> element for drawing graphics; and forms with new input types. HTML 5 aims to simplify HTML and separate structure and presentation, making code cleaner and pages more accessible. It is developed jointly by the WHATWG and W3C organizations.