In your initial implementation, the section hierarchy will consist of a single parent node, called Root. To this single node, you can add as many subsections as you wish, as long as you follow certain rules for section type (see the "Section Types" section). Your products "hang" upon the sections and subsections of the hierarchal tree.

Each site points to a single node of the section hierarchy. This node is known as the site's root section -- the site root section can be either the main (initial) Root node or one of the other main or subsections that you create. In the specialty sites that include the section, the sites' navigation is driven from the first top-level section in the hierarchy.