An order is a collection of information about a purchase or lease. In Purchasing, an order includes information about the purchase (such as order date, order number, price, and so on), as well as the line items that make up the purchase. A single order can include multiple line items.
for example, say you purchased a new CPU. Your purchase order for this item could include the following line items: the CPU itself, a monitor, software, and hardware and software maintenance.