It gives information to the energy; it suggests a direction to take, to leave or to concentrate on a place.
The wind is energy, so nobody doubts its existence, nonetheless we can't see it, we can only see its expression, for example when it makes the leaves move in the trees.
The energy that circulates in a human body is called long Chi, or long energy. We can't see it, and the problems related to it emerge as symptoms or illness.
It travels along channels called Mo, or energy channels, just like blood which travels by the veins and arteries.
Precise points are found along some of these channels, each acupuncture point has a function, thus suggesting an action to the energy circulating in that specific point, zone or area of the body.
In the same way we ask a calculator to do an addition or find a square root.
The result, in the case of acupuncture, is of course the improvement, or upkeep, of the good health of the patient.