Equilibrium:
Occurs at a price which the quantity demanded and the quantity are equal. On a graph, it is where the demand curve and the supply curves intersect.
Disequilibrium:
Occurs at a market price at which the quantity demanded does not equal the quantity supplied
Shortage:
Occurs at any price at which the quantity supplied is less than the quantity demanded
Surplus:
Occurs at any price at which the quantity supplied is greater than the quantity demanded