What does Google even mean when they say that they want it HTML5? Do they want it as a web app? Running inside a WebBrowser control? Do they just want the vi

What does Google even mean when they say that they want it HTML5? Do they want it as a web app? Running inside a WebBrowser control? Do they just want the video to be an HTML5 video tag? I feel there is some very important piece of information missing from this discussion.