ATG Consumer Commerce comes with a default set of product catalog item types that most stores will find useful. These include product, category, and SKU. However, you may find that you need to extend the standard product catalog definition to meet the needs of your site. You may want to add additional properties to the item types included in ATG Consumer Commerce or add new item types that are specific to your needs. ATG Consumer Commerce is very flexible and makes these types of customizations to the product catalog easy to do.