Fulfillment Network Stock Keeping Unit (FNSKU) is an Amazon-unique term to describe the barcodes that help the eCommerce guru identify and track products and connect them to you, the seller. This product-identifying code is similar to a UPC and it’s used to help Amazon label your product in their fulfillment centers.
The UPC is a product identification system used for retail products worldwide, but most commonly in North America. An eight-to-12 digit UPC along with a barcode together make up a UPC barcode, which appears on virtually every retail product.