What is the difference between html and html5?

In breif: New Elements : section, video, progress, nav, meter, time, aside, canvas New Attributes : ping, charset, async, dates and times, email, url.
Full CSS3 Support Video and Audio : support without flash.
2D/3D Graphics Local Storage : ability to store data localy within user browser.
Local SQL Database Web Applications You can read more about it here : HTML5 - Wikipedia HTML5 - Introduction - w3schools

css3

HTML is a markup language that is used to build static (non interactive and nonanimated) webpages.
HTML5 is the latest revision of HTML containing much better support for media like video and audio tags.

HTML5 contains much better support for media such as, an audio and video tag.
The primary one is consistent, defined error handling.
As you know, HTML purposely supports 'tag soup', or the ability to write malformed code and have it corrected into a valid document.
The problem is that the rules for doing this aren't written down anywhere.
When a new browser vendor wants to enter the market, they just have to test malformed documents in various browsers (especially IE) and reverse-engineer their error handling.
If they don't, then many pages won't display correctly (estimates place roughly90% of pages on the net as being at least somewhat malformed).
So, HTML5 is attempting to discover and codify this error handling, so that browser developers can all standardize and greatly reduce the time and money required to display things consistently.
As well, long in the future after HTML has died as a document format, historians may still want to read our documents, and having a completely defined parsing algorithm will greatly aid this.
The secondary goal of HTML5 is to develop the ability of the browser to be an application platform, via HTML, CSS, and Javascript.
Many elements have been added directly to the language that are currently (in HTML4) Flash or JS-based hacks, such as , , and .
Useful things such as Local Storage (a js-accessible browser-builtin sql database, for storing information beyond what cookies can hold), new input types such as date for which the browser can expose easy user interface (so that we don't have to use our js-based calendar date-pickers), and browser-supported form validation will make developing web applications much simpler for the developers, and make them much faster for the users (since many things will be supported natively, rather than hacked in via javascript).
There are many other smaller efforts taking place in HTML5, such as better-defined semantic roles for existing elements ( and now actually mean something different, and even and have vague semantics that should work well when parsing legacy documents) and adding new elements with useful semantics - , , , , and should replace the majority of s used on a web page, making your pages a bit more semantic, but more importantly, easier to read.
No more painful scanning to see just what that random is closing - instead you'll have an obvious , or , making the structure of your document much more intuitive.

HTML5 is simply the latest version of the HTML specification.
It’s much similar to HTML.
But difference is HTML5 contains much better support for media such as, an audio and video tag.

As from wiki pedia HTML5 is a markup language used for structuring and presenting content for the World Wide Web and a core technology of the Internet.
It is the fifth revision of the HTML standard (created in1990 and standardized as HTML4 as of1997)[2] and, as of December2012, is a candidate recommendation of the World Wide Web Consortium (W3C).[3] Its core aims have been to improve the language with support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers and devices (web browsers, parsers, etc.).
HTML5 is intended to subsume not only HTML 4, but also XHTML 1 and DOM Level2 HTML.[2]