Demand is the rate at which consumers want to buy a product and Willingness and ability to supply goods determine the seller’s actions. In economics, supply and demand is the relationship between the quantity of a commodity that producers wish to sell at various prices and the quantity that consumers wish to buy. It is the main model of price determination used in economic theory. The price of a commodity is determined by the interaction of supply and demand in a market. In equilibrium the quantity of a good supplied by producers equals the quantity demanded by consumers.