Some of HTML 5 is here. Smart phones use it, your iPads uses it too.
But first, what is thing called HTML or HyperText Markup Language? HTML is the thing that organizes the information on a web page, like a block of text, or a paragraph, or a column or a list. It also organizes the relationship between these things and how they all work together.
When video, multimedia and interactivity came to the web like YouTube or online games like Farmville everything got very difficult, so there were plugins, applets and many many things like Flash, Silverlight and Java. These things were like trying to put a Porsche engine in a Volkswagen car. Your browser would slow down and you would see that silly circle sign going round and round, waiting until the video loads 100%. It is not how big the file you are downloading; it is slow because of the program behind it. Your computer would start to heat up and the fan would sound like an air conditioner. Not with HTML5 because you can directly insert the audio and the video without any plugins!
Do not bother using Internet Explorer 8 because it is very limited in HTML5. You know why looking at New York Times is great? Or Flipbook? because they are 100% HTML5.
There is another good thing about HTML5, it is about semantics! Semantics is the study of meaning. In web language it is about how you apply meaning to the structure of the web, how you describe the information things contain. For example, a header, a section, a mark like a highlighted text, a time, a navigation is very easy to do in HTML5. You do not have to write a very long code for it anymore.
Enjoy HTML5 !