A catalog represents a collection of products that you group into categories. The categories in your catalogs can have sub-categories, and products may appear in multiple categories. You can define a product with variations, for example, the same shirt can have different colors. These are called a product variants.

Catalogs contain hierarchies and relationships that you use to organize the products in the catalog to make it easier for customers to navigate to the products that they want to buy. You can create category hierarchies and relationships among categories and products that are in the same catalog or in different catalogs.

For example, if you have a large catalog, you can create a parent category that includes several other categories, known as child categories. When customers navigate to the parent category, the child categories appear; enabling customers to navigate quickly to the category that contains the products they want.
For example, you could define an "alternate" relationship so that when one product is viewed, another appears .