Private Catalogs (Fulfillment Account Catalog)
These catalogs pull product information from your fulfillment account. The products in your fulfillment account give you complete control over product images, product pricing, descriptions and so forth. This account is used most often with Company Stores because product images usually require the customers logo to be applied to the product, or the product isn't available in all colors.
A custom catalog takes the existing product information in DistributorCentral and groups them into a catalog. These are products setup by the supplier and they cannot be changed. Everything is updated by the supplier. This catalog type can be used in any website type if the product you add is exactly how the customer will view the product.
Preferred Supplier Catalogs
You can create a group of suppliers to include or exclude from a website with these catalogs. The catalog will effect the ENTIRE product line for the supplier selected, and you have no control of which products within the supplier line to select.