Pump is a mechanical device which converts mechanical energy of its driving unit (electric motor, diesel engine, steam turbine, gas turbine, wind turbine,....etc) into hydraulic energy. This hydraulic energy increases the energy of the pumped liquid and enabled it overcome static head and hydraulic losses in the piping system in which the pump is interposed. The method that is used to supply this energy to the liquid determines the category into which the pump is placed, so there are two types of categories at which the pump can be classified: Roto-Dynamic pumps and positive displacement pumps. We will discuss these types in details in the following article. Pump is an important device that we can't neglect it in our world because it plays a basic role in most industrial applications and also home applications. pump enables a liquid to flow from a region to another region or low pressure to one of high pressure, flow from a low level to a higher level, flow with faster rate, so the function of any pump is increasing the flow rate of the liquid and also increasing the pressure head. pumps are used throughout society for variety of purposes. Early, applications includes the use of water mill to pump the water. Now, pumps are used for irrigation, water supply, gasoline supply, chemical movement, sewage control and marine services. Because of variety of uses of pump, it has much shapes and sizes: from very small to very large, from handling water to handling another liquid , from high pressure to low pressure, from high volume to low volume. Pump is commonly rated by horsepower, flow rate, outlet pressure head in feet or meters and inlet pressure head in feet or meters. The pump material can be stainless steel (SS316-SS304), cast iron etc. It depends on the application of pump.