A catalog represents a collection of products and is usually divided into categories that enable shoppers to browse your products.
The categories in your catalogs can have sub-categories, and products may appear in multiple categories. You can define a product with variations- the same shirt can have different colors. You can also create catalogs that display on your Web site in different languages and different currencies. You can create category hierarchies and relationships among categories and products that are in the same catalog or in different catalogs.