Html Tools just helps you to get a clean, none styled html fo your Google Docs™  content. So you can easily add your content (which is written with Google Docs™ ) into your html page (CMS etc.).
It has a series of options to export your content into html (as "strong" or "b" tag usage etc.). It removes all styles (colors, alignments, sizes etc.), classes and gives you a pure html.
Also has a simple markdown tool to help you.