What are the GTIN and MPN codes?
The GTIN (Global Trade Identification Number) is the international code of your item. It is a unique and internationally recognized identifier for a product. When a GTIN is available, it will appear next to the barcode on your product's packaging or book cover.
In PrestaShop, it will be represented by either the EAN13/JAN code (for European or Japanese products) or the UPC code (for US products).
To know more about GTIN codes, you can refer to this documentation.
The MPN reference is the manufacturer (supplier) reference of your item. MPNs are used to uniquely identify a specific product among all products from the same manufacturer. As far as possible, try to get this reference. It is often on your supplier's invoice or shipping slip when your suppliers ship the product to you.
Please note that if you do not want to export products without GTIN or MPN, you can exclude them by activating the corresponding option in the tab "Product exclusion rules" -> "General exclusion":