Final answer:
Consumer surplus is the extra benefit consumers receive from buying a good or service, measured by what they would have been willing to pay minus the amount that they actually paid. It is used to measure economic welfare.
Step-by-step explanation:
Consumer surplus is the extra benefit consumers receive from buying a good or service, measured by what they would have been willing to pay minus the amount that they actually paid. It represents the net benefit that consumers get from market exchange. Consumer surplus is used to measure economic welfare because it indicates the overall satisfaction and well-being of consumers in a market.