What does this mean?
Means: Bye Flash and bye lag.
First, the <video> tag is already a standard of HTML5, without having to install additional plugins to view the videos (see below). Indeed, the flash only works right on Windows, who use Linux/Mac has to live with the flash consuming half the CPU to see a simple video. Who uses *BSD have to live with the emulation of flash for Linux.
But exists a problem. There is a discussion around <video> tag: “What codec to use?”
We currently have 2 codecs, in one side the free Ogg Theora supported by Firefox, Opera, Chrome and Chromium, on the other hand the proprietary H.264 supported by Chrome and Safari.
Google has chosen H.264, so now the videos can only be viewed in Chrome and Safari.
The new player is still in testing and very incomplete, with no possibility to use full-screen mode, can not display notes, advertisements and videos are converted to low quality. In videos that show advertisements the flash is used (for financial matters :P). Are also a few videos that are converted to the new format, you will have more luck if you try to watch new videos.
How to activate?
Just go to the activation page, enable and ready. Now you can go see the videos :)
See for example the trailer of Besouro(Brazilian Movie).