HTML 5 is a revision of the Hypertext Markup Language (HTML), the standard programming language for describing the contents and appearance of Web pages.
HTML5 was developed to solve compatibility problems that affect the current standard, HTML4. One of the biggest differences between HTML5 and previous versions of the standard is that older versions of HTML require proprietary plugins and APIs. (This is why a Web page that was built and tested in one browser may not load correctly in another browser.) HTML5 provides one common interface to make loading elements easier. For example, there is no need to install a Flash plugin in HTML5 because the element will run by itself.
One of the design goals for HTML5 is to support for multimedia on mobile devices. New syntactic features were introduced to support this, such as video, audio and canvas tags. HTML5 also introduces new features which can really change the way users interact with documents including:
New parsing rules for enhanced flexibility
Elimination of outmoded or redundant attributes
Drag and drop capabilities from one HTML5 document to another
Detailed rules for parsing
MIME and protocol handler registration
A common standard for storing data in SQL databases (Web SQL)
HTML 5 was adopted by the new working group of the World Wide Web Consortium (W3C) in 2007. This group published the first public draft of HTML 5 in January 2008. As of now, HTML5 is in the "Call for Review" state, and the W3C expects that it will reach its final state by the end of 2014.