When procuring materials externally, a purchase order is used. Internal procurement via a production process means that either a production order or a process order is used, depending on the type of production process involved. Procurement via a stock transport process means that a stock transport order is being created when procuring the materials.
A purchase order is created, containing a requested delivery date, and then sent to a supplier. The supplier confirms the receipt of the purchase order. When it is time to do so, the supplier sends to materials towards the ordering company.