HTML5 is to be the next revision of HTML, the core language of the internet, with which websites are built. HTML5 introduces a number of new elements, for example <nav> and <footer>. Other elements provide new functionality through a standardised interface, such as the <audio> and <video> elements.
Part of it's aim is to reduce the requirement for proprietory plug-in applications, such as Adobe Flash and Microsoft Silverlight. A range of new programming interfaces will provide in-built functionality, such as audio and video playback, and document editing.
HTML5 will let you create websites with greater functionality than previous versions of HTML, without needing to turn to proprietory applications to create the effects you require.
HTML5 is currently in draft, being edited by Ian Hickson of Google, and David Hyatt of Apple. Due to the complexity of such a project, it'll take some time to finalise, but you can use some of the features already.
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