Well, ok, I am not officially giving an explanation for how acupuncture works, but I would like to offer you my perspective on how it works.
Most folks have a basic knowledge of how electricity courses through their homes. By simply flipping a switch, light can be turned on and off. Essentially, the currents are like meridians in the body and needles are analogous to light switches.
Acupuncture needles influence the electrical or energetic currents in the body. When energy channels flow freely and in their ideal direction, balance can be restored to the body and illnesses improved.
Acupuncture needles are minute in comparison to medical needles. Patients generally find the experience surprisingly relaxing and may even fall asleep!