Explain how buyers' willingness to pay, consumer surplus, and the demand curve are related

Consumer surplus refers to the amount of product's price which the consumer pays reduced from the total product's price consumer willing to pay. Thus, the consumer surplus and buyer's willingness to pay are related to each other in this sense.

Now, both the terminologies, buyer's willingness to pay and consumer surplus, falls under the demand curve. The full area below the demand curve is buyer's willingness to pay, and area above the equilibrium price refers to consumer surplus. Thus, these three are closely related to each other.