With HTML5, they took it all apart and started from scratch. For years we’ve been using general containers for specific elements (headers, footers, etc.), and styling those elements based on their arbitrary class or ID name.
But with HTML5, we no longer need to do that. Along with a ton of new tags, HTML5 falls back to those general elements should the user be viewing your site or app on an older browser.
HTML5 boasts a ton of new tags from HTML4. HTML5 code is much cleaner and easier to read.
HTML5 was built with mobile in mind. It's the language of the future.
With simple code comes higher standards. Living up to these standards, however, is much easier.
HTML5 was made for the future, is easily adaptable, and molds to any web app.
There have been countless work arounds for animating and creating / using space on the web. Thanks to the HTML5 canvas element, we no longer need to do this.
Canvas allows us to create animations and, essentially, drawings right within our HTML. Using some simple markup, this is all possible, and mobile friendly with HTML5.