Many channels require or recommend various product IDs. We have compiled the below list of common product IDs and their definitions. 

• SKUs (stock-keeping unit) also called Unique IDs are assigned by the merchant; for internal identification of inventory and sales.
• MPN (Manufacturer part numbers) are assigned by the Manufacturer; a static Identifier of a product which is universal to all distributors, wholesalers, resellers. This can usually be found near the UPC number on the box or label.
• UPCs (Universal Product Code) are assigned by the Manufacturer; always 12 to 13 digits.
• ISBN (International standard book number) is a ten-digit number assigned to every book before publication, recording such details as language, provenance, and publisher
  
• GTIN (Global Trading Item Number) is an umbrella term used to describe the entire family of EAN/UCC data structures for trade item identification. In addition to the UPC and EAN, it also includes the EAN/UCC-14 code that is used to identify packaging levels. This term replaces the barcode no.
• GTIN/UPC/ISBN Resources:
  • GTIN INFO
  • UPC DATABASE
  • ISBNdb