A circular flow model describes how money, resources, and goods (or services) move from households to corporations and back again. On one side of the model, we have the product market. Corporations make products or provide services that they sell to households (or the government or foreign markets) for money.
On the other side of the model, we have the resources market. Households provide resources to corporations, especially in the form of labor, in return for wages, which are then used to purchase more products in the product market. The resource market also includes the exchange of money for land or raw materials needed to produce products.
Let's look at an example. A family is shopping for a new computer. They do a lot of research and determine the best machine for their needs, and they then order it online and pay for it using a credit card. The computer manufacturer obtains the money paid and ships the computer to the family. This is what happens on the product market.
On the other side of the circular flow, we have what happens with the computer manufacturer. To produce computers, the company needs raw materials (plastic cases, computer chips, etc.) that it purposes from other manufacturers. It also needs land for a factory (which it already has), and it needs labor (so it pays wages to workers from households). This is the resource market.
If the father of the family who bought the new computer actually works for the computer manufacturer, the two markets combine in him. He receives wages from the computer manufacturer (selling his labor on the resource market), and he uses part of those wages to purchase the new computer (in the product market).