GTIN (Global Trade Item Number) – Specifies the unique code of the packaged product or service. The name GTIN defines the entire family of identifier structures developed by GS1. These identifiers can consist of a different number of digits (8, 12, 13 or 14).
GS1 – A non-profit organisation that standardises rules and guidelines to improve operations in supply chains.
More information you can find in here.
How can you add a barcode on your Online Store admin panel?
For example, you can add codes such as GTIN, ISBN, etc. when adding a product or editing it.
When adding a new product, enter it in the Barcode field
If your product has variants, then each of them will have a separate code.
Go to Products > Select a product > Variant Section > Barcode .