Basically it's a Markdown to HTML processor, pre-packaged with BootStrap Bootswatches. And some extra tricks :

• A header section that lets you define a menu, footer, projectname, bootswatch, head_extra (extra code to put in page headers)
• A "page-break" option so that your single .md file becomes a number of HTML pages
• A very light-weight markup for defining divs with classes and ids using [.CLASSNAME#ID and .]
• A markup for including CSV files as tables.

Unlike most static site systems that are built around templating engines, with BootDown you write both your page content, and the structure in a single source file. Using [. .] for divs. This gives you all the flexibility you need to layout your pages any way you like, within the BootStrap grid.