What is the difference between 'document' and 'non-document' or 'product' shipments for international shipping?

The difference between document and product is straightforward but important.

A document shipment includes paper of little or no commercial value (e.g. business correspondence) and generally doesn't require a Commercial Invoice.

A non-document or product shipment defines all other shipments and printed materials of value. Examples include clothing, automobile parts, sports equipment, books, etc. All non-document international shipments require a commercial invoice.