In loyalty programs, Odoo needs a way to recognize which customer is using a loyalty card or reward program. For this, Odoo commonly uses a barcode identifier linked to the customer or loyalty card.

When the barcode is scanned in POS or used during the sale, Odoo can identify the related customer/loyalty card and apply the available loyalty points, rewards, or benefits.

So the identifier is not mainly the customer name, email, or phone number. The specific identifier used for loyalty recognition is the barcode.