DNN uses templates and skins: templates are used for creating new sites, starting with a predifined set of pages and modules, skins are used to manage the layout of the pages with panes for modules and a graphic design, while the modules are skinned by containers, that determine the look of the modules and portal driven controls like action menu, print icon, min/max, ...

Skins and containers can be created using tables or divs, have a look into the skinning guide that is part of the documentation pack, which you can download from the download page.