Equillibium

Equilibrium- is the point at which the supply curve and the demand curve intersect.  At this point, all resources are being efficiently used.
 
Excess demand- occurs when the quantity demanded is greater than the quantity supplied.  This will result in shortages, where consumers cannot get the quantities of items that they desire.

Excess Supply-when the quantity supplied is greater than the quantity demanded, creates surplus

Price ceiling- creates a shortage and occurs when the government puts a legal limit on how high the price of a product can be.
Excess supply- occurs when the quantity supplied is greater than the quantity demanded.  This will result in a surplus, where producers have inventories they cannot get rid of.
 
Price floor- is the lowest legal price a commodity can be sold at. This creates a surplus and is used by the government to prevent prices from being too low.