Supply and demand are both very important to economic activity. Supply is the total amount of a particular good or service available at a given time to consumers at a given price.
Demand is a representation of a consumer's desire to purchase goods and services; it acts as a measurement of a consumer's willingness to purchase a specific good or service at a given price. These two economic forces influence each other; they are both important for the economy because they impact the prices of consumer goods and services within an economy and the quantities produced and consumed.