You don't. However, it does come with HTML5 and QuickTime installed.

It doesn't matter. Modern browsers will play video in HTML5.

Syntax is very similar. HTML5 allows you to upload video, do animation, etc. without the use of Flash or Silverlight. Pretty awesome...

Not every animation on the web is Flash but currently the majority is. There exists simple GIF based animations as well as other technologies for animation such as Silverlight and HTML5. Most believe HTML5 will eventually replace Flash. If you right click on an animation and see a context menu choice about Adobe Flash Player then it is a Flash animation.

People are saying HTML5 will simply take over Flash instantly. This isn't going to happen. HTML5 still is behind Flash in the number of features, and will be for years. HTML5 isn't yet compatible with all browsers, and it never will be, assuming Microsoft, Google and Firefox start forcing browser updates.

HTM L5 is actively working with JavaScript in many ways, such as Geolocation and Canvas.

There is heaps you can do with HTML5, all you need to do is use a search engine to see whether what you want to do is possible.