If you break down any transaction, it has three components. First, there is the agreement to trade some goods and services for some price. At this moment two debts are created. One is to deliver the money. The other is to deliver the goods and services. The 2nd and 3rd component is the delivery of the money and the delivery of the goods and services.

If you for a candy bar in cash all three happen at the same time. When you buy something and pay later, or pay up front and get something later, it’s easier to see the different components. When you buy stocks via a broker, it’s even more apparent.