The law of rent tells us how much people are willing to pay for land. That means that if there is some land that is really nice, then people will be willing to pay more for it than for land that isn't so nice. For example, if there's a big park near a house, then the house would be more expensive than the same house that isn't near the park. So, the law of rent tells us how much people will pay for land depending on how nice it is.