Consumer Surplus – The difference between what a consumer would be willing to pay for the units purchased, total value, and what the consumer actually pays, total expenditure; graphically, the triangular area under the demand curve and above the market price.

Producer surplus (rents) – The difference between the minimum total amount producers must be paid in order for them to voluntarily offer a given quantity of a good for sale and what the consumer actually pays for this quantity; graphically, the triangular area above the supply curve and below the market price.