PI equals to proforma invoice refers to an abridged or estimated invoice sent by a supplier to a drop shipper in advance of a shipment or delivery of goods. It notes the kind and quantity of goods, their value, and other important information such as weight and transportation charges.
CI equals to commercial invoice refers to a document used in foreign trade. It is used as a customs declaration provided by the person or corporation that is exporting an item across international customs.
PL means packing list: It is a shipping document that accompanies delivery packages, inside an attached shipping pouch or inside the package itself usually. It normally includes an itemized detail of the package content.
PO means purchase order: It is a commercial document and first official offer issued by a dropshiper to supplier, indicating types, quantities, and agreed prices for products or services.