Difference between Html and Html5
HTML5! - the exciting web phenomenon - is really an attempt of the browser vendors (and W3C) at making all the features of desktop apps, Flash - and anything that previously needed a browser plugin - an integral part of the browser standard itself. The browser has become a sandbox for application development, whereas it was previously a platform for installing application development tools; something which often broke, angered/confused or opened security holes.
It's worth noting that HTML 5 (the updated specification) hasn't formally been agreed yet. That hasn't stopped progress, however, the de facto 'standards' in HTML, CSS and JS are being rolled out continually, thanks to the new generation of 'evergreen' browsers (e.g. Chrome/Safari/Opera, FireFox and IE11). The timing of HTML, CSS and JS progress is somewhat coincidental (driven by demand), but it's a great relief to developers that these things are coming together.
The web is the new host platform and HTML5! is the new Operating System.