Pumps are devices that use mechanical energy to increase the velocity, pressure, or elevation of liquids and gases. There are two main types of pumps: positive displacement pumps and dynamic pumps. Positive displacement pumps apply pressure directly to the fluid using reciprocating or rotating components, while dynamic pumps like centrifugal pumps use rotation to impart kinetic energy and convert it to pressure energy. Common positive displacement pump types include piston pumps, plunger pumps, gear pumps, lobe pumps, screw pumps, and diaphragm pumps. Centrifugal pumps are widely used dynamic pumps that contain an impeller and casing and work by accelerating fluid outwards from the center of rotation.