Explain the idea of consumer’s surplus

Consumer surplus: Consumer surplus is a measure of the welfare that people gain from consuming goods and services.

Concept of consumer’s surplus is a very important concept in economic theory, especially in theory of demand and welfare economics.

Marshall defines the consumer’s surplus in the following words:

“Excess of the price which a consumer would be will to pay rather than go without a thing over that which be actually does pay is the economic measure of this surplus sates faction, it may be called consumer’s surplus.”

Consumer’s surplus = what a consumer is willing to pay minus what he actually pays = 

The concept of consumer surplus is derived from the law of diminishing marginal utility. Consumer surplus is a measure of the economic welfare that people gain from purchasing and then consuming goods and services.

Consumer surplus is the difference between the total amount that consumers are willing and able to pay for a good or service (shown by the demand curve) and the total amount that they actually to pay (I.e. the market price).

Consumer surplus is indicated by the area under the demand curve and the market price.