A bill of lading is a receipt, a contract, and a set of instructions required to move shipments. The person who is shipping items must provide the carrier with a bill of lading. This legal document describes what is being shipped, to where, special instructions, information required for billing, and a title of goods (to be transferred by the carrier to the entity receiving the shipment).
In the US, bill of lading refers to any kind of shipment, but in British English the term is used exclusively for cargo loaded onto ships. A bill of lading has been used for trading since the times of the Ancient Romans and is used internationally in one form or another.
This makes it an important part of international trade. A bill of lading is both a tool for the carrier to do their job properly and a document used to settle legal disputes that arise from trading issues.
The bill of lading is a vital part of trucking, as is having proper commercial roadside assistance.