A pump is a machine which moves a liquid from one place to another, often upwards.
Pumps need some kind of power, often kinetic energy, to make them work. Sometimes the power comes from a person. Sometimes the power comes from a motor.
There are many different kinds of pumps. Some types of pumps are:
Drawing of the inside of a metering pump head to show how it works. The piston
moves back and forth inside the pump head.