Brad Neuberg’s video on HTML 5 gives a very thorough overview of HTML 5.  This video is approximately 40 minutes in length.

The video covers 5 main topics:

1. Vector Graphics
2. Video
3. Geolocation
4. App cache and database
5. Web workers

Overall, HTML 5 has improved on previous versions of HTML in the areas of graphics, location, storage and speed.  It is more powerful.  And there is a tremendous improvement in Javascript performance.

Vector Graphics

Prior to HTML 5, you could not draw or have any interactive content unless you used applications such as Flash or Silverlight.  In HTML 5, SVG and the Canvas API are  now embedded into the DOM.

SVG (Scalable Vector Graphics):  You now have tags for drawing graphics.

Canvas API:  This is the javascript API.

Video

HTML 5 now gives you a video tag for embedding video.

Geolocation

Geolocation is now built into the browsers.  For determining the location of the user you can use GPS, IP, Cell ID or WIFI information.

App Cache and Database

If you are going to build a web app, it needs to work anywhere and at anytime.  This new feature helps provide off-line web access.

App Cache is basically super browser cache.  It brings all of the information locally.  You can now create a user interface that can be brought offline.  This will require the user to grant permission to save the data to a local database.  In addition, since the browser can crash or disconnect at any given time, everything needs to be a transaction.

Web works

This lets you to run javascript in the background. Currently, if you start running javascript that is very computationally intensive, it can hose the browser.  Web works allow you to run this javascript in the background and allow the user to continue to interact with the web app.

HTML 5 is currently supported to some extent by the open source browsers such as Chrome, Firefox and Opera, as well as Safari.  It is not supported fully in IE 8.  You will have to wait until it is supported in IE9 before taking full advantage of it.