Each product variant can have a separate Barcode, ISBN, or UPC. This field is not to be confused with the product SKU, which is the internal code used to reference each product variant.
Barcodes are the most common type of UPC (Universal Product Code) that we’re all familiar with. Each barcode has it’s own unique number associated with it, which you can enter into this product field.
ISBNs (International Standard Book Number) are 10 or 13 digit numbers assigned to each edition / variation of a book. For example, an e-book, a paperback and a hardcover edition of the same book each have a different ISBN. They are used as a universal system of tracking book sales. You could also enter the ISBN into this field.
Basically this field on Shopify allows you to assign another unique code to each product variant. Or you can leave the space blank.
I guess Shopify wins here since Lemonstand doesn’t have this field. Since Lemonstand is highly customizable, I researched how to add a Barcode, ISBN, UPC field for each product variant on but I did not find the solution. As you know, I’m not nearly as familiar with Lemonstand as I am with Shopify, which is why I made this website (to help me learn the differences). I added this issue to the Questions page and will follow-up with Lemonstand later on how to accomplish this.