HTML5 is the most recent version of Hypertext Markup Language. This involves using HTML to provide the structure, JavaScript to make things happen and CSS to help the presentation.
HTML5 is desinged to deliver just about everything you wanted to do online in which you do not have to add plugins to browers. From animations to applications, music to movies, it is complicated but it is possible to run these in HTML5.
To run HTML5 you probably already have what is needed to complete this. A big name browser like Firefox, Chrome, Safari, (*Explorer and Edge dosen't count but supports it*) support HTML5 but they do not all support the same thing. FIrefox generally support he most selection of HTML5 and Chrome.
HTML5 is an evolving and it is a bit misleading. As it keeps evolving a new rendition may come out in the new future. GEO location, webapps and video graphics can be used by your browsers.