I get asked this question a lot! There are several prominent theories and many studies showing how one or more points affects a particular system, but no cohesive theory that can explain every point action.
What I believe is that different points function by different mechanisms, based on their body location. Many of the theories about how acupuncture work are based on studying one or another major points, but not all point locations are similar to each other.
When most people think about acupuncture, they are familiar with its ability to control pain. However, acupuncture has a proven record of treating a variety of endocrine, circulatory, and systemic conditions. Over the last few decades, research has been conducted seeking to explain how acupuncture works and what it treats. Below I summarized it as I could, but if you dont want to read more, here is the short list.