A pump in general is a machine which imparts energy to anything flowing through it. This can be any fluid, heat or even electrons. The devices pumping heat are called as heat pumps and electrical batteries can pump electrons. The spontaneous tendency of anything is to flow from high potential to low potential and this natural tendency is harnessed in many applications. But the pump does exactly the reverse; it forces something to move from low potential to high potential. For this purpose pumps use energy and by their functioning transfer that energy to the substance flowing through them.
Fluid pumps or Hydraulic pumps move fluids and displace them from one position to another and in course energizes them. In fluids this energy is manifested as its pressure and velocity. Similarly, heat pumps move heat from low temperature to high temperature against its natural tendency to flow from high temperature to low temperature. An electrical battery is also a type of pump; it pumps electrons in a circuit from low electrical potential to high electrical potential which is against the spontaneous tendency of electrons to move from high electrical potential to low electrical potential. Hence, an electrical battery can be called as an Electron Pump.