Shipping order is a derivative of Purchase Order for a specific shipping option.
Shipping order is automatically generated with a unique shipping order number when a purchase order is confirmed and payment is made successfully. Each shipping order has a specific shipping option to instruct merchant the method to ship products.
Multiple shipping orders are possible to have been derived from one purchase order that has multiple shipping options.
Merchant (or seller) work on shipping order for order fulfilment, i.e. one fulfilment per each shipping option.
It carries the same information as purchase order does but with one shipping option.