Drop shipping is where a store or the seller does not keep or have the product in stock. When a sale is done the seller then purchases the product from a third party who then send the product to the customer direct. Drop shipping is massive for online stores or e commerce as you dont need storage to store your goods. In effect anyone can set up a drop shipping store. The drop shipping method does put a lot of risk into your supplier, if they muck up on their end your customer will not be impressed. Slower shipping is also a problem as the product is not local.