The Marketplace
Since 1995, the number of sellers has grown, the types of sellers have grown, and the product offerings have grown. All of these sellers come together to sell their items on www.amazon.com, in what is called the "marketplace."
Individual sellers cannot have their own storefront in the marketplace. Pro Merchant Sellers and Merchant@ vendors can. Individual sellers can, however, set up their own storefronts outside of the marketplace. These storefronts can be accessed through www.amazon.com. Amazon refers to these stores as zShops.
Product Advertising API requests cannot access zShops. This usually has little impact on product searches because zShop owners can also list their items for sale in the Amazon marketplace.