Consumer surplus refers to the difference between what consumers are willing to pay for a product and the actual price they pay. Willingness to pay refers to the maximum amount that a buyer is willing to spend on a good, representing the value they place on it. The price they actually pay is the market price of the product.

Consumer surplus is a measure of the economic benefit consumers receive when they purchase a product at a price lower than the maximum price they would be willing to pay. It represents the excess satisfaction gained from purchasing a good at the market price. 

For an individual, this surplus reflects the extra benefit they derive from purchasing a product for less than their maximum willingness to pay. For example, consider Sarah, an avid reader, who wants to purchase a novel from her local bookstore. Sarah is willing to pay up to $20 for this novel due to her love for the author and the joy of reading. However, the bookstore sells the novel for $15. In this situation, Sarah's consumer surplus is $5—the difference between her willingness to pay ($20) and the actual price she paid ($15). 

Sarah’s $5 consumer surplus reflects the additional satisfaction or value she gains from the transaction. While the market price is $15, Sarah values the book more highly, making the $5 difference a quantifiable measure of her surplus enjoyment. 

This surplus is not unique to Sarah but applies to any consumer when the price of a product is less than their willingness to pay for it.