A more thorough explanation:

A pumping unit is a piece of equipment used in the oil and gas industry to pump oil to the surface. It is used when the pressure difference between the formation and the borehole is not strong enough to cause oil to rise to the surface.

Another term for a pumping unit is a pumpjack or horsehead.

For example, if an oil well has low pressure, a pumping unit can be used to extract the oil from the well. The pumping unit is placed on top of the well and uses a motor to drive a series of rods that move a piston up and down in the well. This creates suction that pulls the oil to the surface.