Consumer surplus is a measure of the difference between the amount that a consumer is willing to pay for a good or service and the actual price that they pay. It is essentially the benefit that a consumer receives from a transaction, over and above what they actually paid for it.

For example, if a consumer is willing to pay $10 for a cup of coffee, but they only have to pay $5 for it, then their consumer surplus is $5. This means that they received $5 worth of benefit from the transaction that they did not have to pay for.

Consumer surplus is important because it helps to measure the overall welfare of consumers in an economy. When consumer surplus is high, it means that consumers are able to buy goods and services at a price that they consider to be reasonable, which leads to higher levels of satisfaction and well-being. On the other hand, if consumer surplus is low, it may indicate that consumers are facing high prices or other barriers to accessing the goods and services that they need.