The Product SKU is the SKU that LM uses to keep track of a listing.
The Marketplace SKU is the SKU that exists on the marketplace.
These do NOT have to be the same. If they are not, the marketplace SKU will show up as the alternative SKU under the prodduct SKU on the Manage Listings page. See image.
In the above image, the SKU on Amazon is fest-fba-sku-8. The Product SKU is fest-sku-8. LM knows all of these products are the same one, spread out across the different channels.
Note, you can NOT find a listing by searching for the alternate SKU. You must find the listing by searching with the product SKU.
This difference will not matter to Listing Mirror. Even when you receive an order from a marketplace, where the SKU on the marketplace does not match the Product SKU, LM will still know which item it is. In the Order Details page, you will see both SKUs listed.
**Due to ongoing changes, the Master SKU referenced on the orders page is referring to the Product SKU**