Smith assumes that in this system, money serves almost entirely as a means of payment or unit of account. He doesn't imagine market participants seeing money as a form of wealth they could or should accumulate (as we would today). This leads him to assume that people will not hold money as a store of wealth, but will spend it, keeping the circular flow going.
characterising Smith as the first classical economist (differs from predecessors in that it concerns itself wih the whole nation, not just the monarch's coffers)
also: he implies that price serves as a signal to producers, and that the state doesn't need a big role (other than to protect the nation, enforce the law, and provide some public goods)