HTML5 doesn’t just improve the process of creating applications, it improves the fundamental functionality of your web page by making activities smoother and more intuitive. For those of us who live and breath mobile, the new specification certainly portends to be a game changer that can deliver browser based applications that can rival native application performance.
"It stands strong and true, resilient and universal as the markup you write. It shines as bright and as bold as the forward-thinking, dedicated web developers you are. It's the standard's standard, a pennant for progress. And it certainly doesn't use tables for layout." (Source w3.org)
Here's a quick (digestible) summary of the key elements that the new spec. offers (in no particular order):
3. Local storage
Increased functionality for storing web based information locally on your machine - important for data dependent web applications aimed at the enterprise. This also allows for allow websites to store information across sessions, which improves performance and reduces server-side queries.
4. Web workers
Web workers defines an API for running scripts in the background independently of any user interface scripts (without tying up the UI) - essentially allowing for smoother running of code-heavy web pages.
Enables location (generated via GPS, cell-tower triangulation or wi-fi databases) to be available to any HTML5 compatible browser-based app.
6. Semantic document structure
A new semantic structure for pages which was previously handled using DIV, SPAN, and other elements with class and ID attributes - these elements include Header, Nav, Article, Selection, Aside, and Footer.
7. Client-side database
The client-side database API interface features enable access to local databases with an SQL server built into the client (sometimes referred to as a local SQL database). Database capabilities will allow for a broad range of consumer and business oriented browser-based mobile applications.
8. Cross document messaging
A very useful feature that allows documents on different domains to communicate with each other (e.g., enabling two frames with content from different domains to communicate).
By the way, you can even get an official HTML5 t-shirt and a bumper sticker (free) at w3.org! I would also suggest poking around and checking out the new w3.org site design as well.