Why are there different versions of HTML?

it think the versions are

HTML 1.0

HTML 2.0

HTML 3.0

HTML 3.2

HTML 4.01

xhtml 1.0

and now HTML 5

The different versions are used to characterize changes in the HTML itself. With new features and new tags come new versions. In the modern web, (HTML 4+) the versions are also the basis for laying out standards that describe the function of the HTML and how the browsers are supposed to display it.

For instance, prior to HTML 2.0, there were no images available in HTML.

If you're interested, the W3C (World Wide Web Consortium) is in charge of keeping the current HTML and XHTML standards. You can find the specific changes in versions on their website.