HTML5 is a loaded term that covers a range of ideas, but here is an attempt to explain it. Explicitly, all that HTML5 stands for is the next version of HTML. After this version there will be no more versions of HTML. Instead they will evolve the spec slowly over time instead of using major revisions. The next gold standard was going to be XHTML2, but it got dumped because it was built on an unrealistic view of the web. The view was that the web could be a place that used perfect syntax if only you forced it to. A bunch of standards makers broke away from the W3C, and created the WHATWG which gave birth to, among other specs, HTML5. It’s goal was the re-think how to derive standards, and it chose to look at how the web worked currently, versus what it could be. For that reason HTML5 has a lot of elements that we have today, but they have been codified some how. One example is progress bars, currently they are implemented as a hack, in HTML5 there is a progress bar element.
The bottom line is, HTML5 is going to be broadly accepted, and broadly distributed. It’s time for web developers to cheer, and it should make developers of other platforms weak in the knee’s. If a device has a HTML rendering engine it’s going to have HTML5: computers, phones, tablets, TV’s, and, yep, even cars. Some may dismiss HTML5 as a toy, but they are being shortsighted. For every nearsighted prognosticator there are a dozen web developers, who don’t care about the platform wars, and instead just want to make apps. HTML5 is the logical next step for them. Even billion dollar companies are gearing up to invest big in HTML5. Wherever you fit in your organization, lone wolf, or CEO, HTML5 is what’s next.