Product storage represents the act of warehousing inventory over a period of time. All SKUs, cross docks, freight shipments or forwarded shipments that stay in a warehouse for over a day are being stored.
Fulfillment houses charge storage on shipments or inventory in their warehouse. This storage can be calculated on a daily, weekly or monthly basis. Often a grace period will be given for cross dock and freight shipments so that those simply passing through do not get charged for storage.