A pump is any device meant to facilitate the motion of a fluid. Pumps displace fluids, causing it to move down or out of a pipe. Most pumps use some sort of compressional action to displace the fluid. This compressional action sometimes necessitates a motor that acts to put pressure on the fluid in order to displace it. This motor can be powered by a variety of fuels, as long as it has the necessary power to displace the fluid. Most pumps are either positive displacement or rotodynamic.