Answers (2)
HTML5 is just the newer specification for HTML.
As for which one is better, HTML5 is now fairly widely supported amongst browsers. It's got some pretty cool features like support for audio and video, 2d drawing using the canvas element, new semantic elements and much more.
We can differentiate as:
HTML -> Audio and Video are not part of HTML4 specification.
HTML5->Audio and Videos are integral part of HTML5 specifications e.g. <audio> and <video> tags