The html site map is one more special static page. You will see all of your static pages here in the tree view. So for example if you have got the following pages:
index.html arsbuilder/index.html arsbuilder/faq.html terms/licence.html
You will see the index.html in the root section of the html site map, and the arsbuilder and terms sections will be created too. The “arsbulder” section contains the index file, so the title of this section will forward your visitors to index page. But the “terms” hasn't got the index file, in this case the title of the section won't be defined and the links from the terms directory will be simply listed in the separate dir.