Jay covered it well but if you don't have power to the fixture at the pole there could be another reason. If you have an underground line that runs up the pole, ground movement from the hot dry spells we are having (especially with clay soil when it dries up) can pull the wires loose from their connection. It is more common around here with phone lines but I would check the wiring in the fixture also. If this is a yard light with a day/night detector to turn it off, this could have gone bad also.