A more thorough explanation:

Definition: A pumpjack, also known as a pumping unit or horsehead, 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.

Example: Imagine a well that has been drilled into an oil reservoir. If the pressure in the reservoir is not strong enough to push the oil to the surface, a pumpjack is used to extract the oil. The pumpjack is placed over the well and uses a motor to drive a series of rods that are connected to a pump at the bottom of the well. The pump then lifts the oil to the surface.

Explanation: The example illustrates how a pumpjack is used to extract oil from a well when the natural pressure is not strong enough to bring the oil to the surface. The pumpjack is an essential piece of equipment in the oil and gas industry, allowing for the extraction of oil from wells that would otherwise be unproductive.