Supply and Demand Curves are the curves that show what is the supply of a good or a service at a set price and in a similar way, what is the demand for this good or for this service at a given price. The demand curve intersect with the supply curve at the point where demand and supply are equal. If the demand is higher than the supply, then the price goes up and in a similar way, if the supply is higher than the demand, the price will go down.