Acupuncture involves stimulating body walls like skin and muscles to produce therapeutic effect. It can be used for a very wide range of conditions: Acute pain, chronic pain, respiratory conditions, skin problems, gastric problems, etc.
If you can imagine your body is a city, so in the city there are big roads, highways, there are small roads, there are lane ways. So if everything is fine, traffic goes nicely. But if a car breaks down, then the traffic will be jammed up. And if the broken car is not fixed, the traffic jam will become worse and worse. Let's imagine in the body there are meridians. And in these meridians we have chi flow, we have energy flow. So for instance if you hurt your back, the local muscle will become very tight, and this kind of tightness is the way of blocking the chi flow. This is where acupuncture comes in.