This tool is designed to be embedded within an XSLT processing pipeline. html2html.xslt can be used in a custom stylesheet or integrated into a larger system. See Overriding.
The output can be customized by the means of additonal markup in the XHMTL source. See the section on customization.
h1, h2, etc. are turned into nested section and title elements (as opposed to bridge heads).
In particular, html2db.xsl automatically wraps naked item text (text that is not enclosed in a <p>) inside a table cell or list item. Naked text is a common property of XHTML documents, but needs to be clothed to create valid Docbook.