Commerce Reference Store extends the catalog item descriptor with one property called rootNavigationCategory. The rootNavigationCategory property is of type category and it references the rootCategory category. rootCategory functions as the root of the navigable category/product tree. It is a sibling of the NonNavigableProducts category, which provides a location for organizing products, such as gift wrapping, that are non-navigable (that is, not part of the category tree). Neither the rootCategory nor the NonNavigableProducts category is visible to a website visitor.