With each upload, all existing products are updated and new products are added. All products which have not been re-uploaded during the latest import are marked as deleted. They are not completely erased from our database, however they are flagged as inactive. Therefore, if you wish to keep these products active, please make sure you upload them during each import.
Important: Uploading the product feed with with several new products will result in deletion of all your existing products. Your product feed will then contain only those new products you imported with the last product feed.