Categories and products are the heart of the catalog structure. Categories organize your catalog into a hierarchy that provides a navigational framework for your commerce site. A category can contain other categories, products, or both.
For example, you could have a category called Fruit, which contains two products, Apples and Pears, and also contains another category, Citrus Fruit. The Citrus Fruit category could then include products called Lemons, Limes, and Oranges.
A product is a navigational end-point in the catalog. In this example, Oranges is an end-point; it cannot contain other categories or products. However, products do not represent the items that customers actually purchase. The purchased items are called stock keeping units (SKUs). A product can have several different SKUs associated with it, representing different varieties, sizes, and colors. For example, if you have a product called Oranges, some of the SKUs associated with it might be Valencia, Navel, and Blood Orange. For more information about SKUs, see SKU Items and SKU Links later in this chapter.
The hierarchy defined by products and categories is not rigid. Each category or product can be the child of one or more categories.
