A Purchase Order is a legally binding document that is issued by a buyer to a seller, indicating the type, quantity, and agreed-upon price for products or services that the seller will provide to the buyer. This document serves as a contract between the two parties and is legally binding, meaning that both parties are obligated to fulfill the terms of the purchase order. It is important to note that the purchase order is not the same as an invoice, as an invoice is sent after the products or services have been delivered, and is used to request payment from the buyer. The purchase order, on the other hand, is sent before the products or services are delivered, and is used to specify the details of the transaction.