ASIN (Amazon Standard Identification Number) is an existing number consisting of 10 characters (letters and/or digits) to identify products on the Amazon platform. The ASIN is created when a product is loaded into the directory of Amazon. The ASIN code identifies the model, the color, and the size of the product. SKU (Stock Keeping Unit) is for identifying products in stock. All products, added by Amazon, have to own an SKU number. You can add the SKU number by yourself. Otherwise, Amazon will assign an order of random letters and digits to your product. FNSKU (Fulfillment Network Stock Keeping Unit) is a code, which you can generate in your sales panel. The number will be assigned to the products of a certain seller. Like the SKU code, the code consists of 10 characters (letters and/or digits). This number allows identifying products inside the warehouse of Amazon as a product of one single seller. GTIN (Global Trade Item Number) is a barcode assigned by the manufacturer to the product. Primarily, it is for determining the manufacturer of the product. The GTIN code also identifies the country of origin and sometimes the weight of the product as well. The GTIN codes confirm the legality of your products. The regional equivalent to GTIN codes is the EAN (European Article Number).