An inventory item is "archived" if the listings have been deleted from Amazon Inventory and are no-longer returned in the inventory reports.

With that setting "Restock Archived Inventory" checked in Settings >Prep & Ship > Listings, it allows you to pull up those old SKUs and list them although you may need to create listings for those SKUs again.

If the setting was not Selected /Checked, ScanPower will not pull in those old SKUs when finding existing inventory when listing/adding item to the batch.