An order, in business, is a stated intention, either verbal or in writing, to engage in a commercial transaction. From a buyer's point of view it expresses the intention to buy and is called a purchase order. From a seller's point of view it expresses the intention to sell and is referred to as a sales order.
In many businesses orders are used to collect and report costs and revenues according to well-defined purposes. Then it is possible to show for what purposes costs have been incurred.
See also