What does it mean to "truck, barter, and exchange?"

A fairly quick search suggests that "Truck" in this sense is from the Old French 'troque,' which actually means to barter or trade. It seems to have extended to actual produce produced for sale and from there to the system of paying in goods or tokens but I can't see what distinction Adam Smith was drawing between the the three terms.

Down with Truck, Barter, and Exchange! ... It is the necessary, though very slow and gradual, consequence of a certain propensity in human nature which has in view no such extensive utility; the propensity to truck, barter, and exchange one thing for another