A pump is a mechanical device that uses mechanical action to move fluids from one place to another. There are two main types of pumps: positive displacement pumps and hydrodynamic pumps. Positive displacement pumps work by trapping a fixed amount of fluid and forcing it to the discharge side, including types like reciprocating pumps (piston pumps, plunger pumps, diaphragm pumps), rotary pumps (gear pumps, screw pumps, lobe pumps, vane pumps). Reciprocating positive displacement pumps include piston pumps, diaphragm pumps, and plunger pumps. Piston pumps can be further divided into types like axial piston pumps and radial piston pumps.