The intersection between the upward sloping function (the supply curve) and the downward sloping function (the demand curve) is the equilibrium price of the market, the point at which the wishes of consumers and suppliers meet.
The graph described should be like the one attached. The example includes the demand and supply curves and the equilibrium price of a market of agricultural products.
When the economic authorities set a minimum price (also called price floor), above the equilibrium price there is a situation of excess supply.
The wishes of producers and consumers do not meet in the price floor situation, the quantity supplied is larger than the quantity demanded and therefore there is an excess supply.