multipack: if you’re selling a group of individual products as a single unit, like a 6-pack of scented candles.MPN: if your new product does not have a manufacturer-assigned GTIN (one exception is if you’re selling custom or handmade goods in this case, you wouldn’t have an MPN or GTIN).GTIN: if your product has an assigned Global Trade Item Number assigned by the original manufacturer.
Next, if you sell anything other than books, music, and movies, Google has some additional fields that you’ll need to include in your feed, such as
Google Shopping has some of the highest potential to generate massive sales.