By default, the module synchronizes your offers, we speak of sync by abuse of language, but that’s not the subject.
If your offer is an offer on Amazon, so if the reference of your product on Prestashop is the reference on Amazon (SKU) then the offer is updated, the quantity, the price (…).
When you do not have this reference on Amazon, the module can send the offer including the EAN or UPC code at that moment Amazon searches a product corresponding to the code and creates an offer corresponding to your inventory, that is the “matching”.
Amazon has found a match between your EAN/UPC code and a product of its database so creates an offer with your SKU.