Cupping is a cleansing technique often practiced by Oriental Medical Practitioners. It helps to break up congestion and relieve pain in the area being treated. It can be especially useful for persons with edema, asthma, arthritis, and other painful or congested placed on the body. I have seen it done most often on the back.
A vacuum is created in small jars/cups using a candle or a special machine (made for this purpose). These cups are then placed on the area being treated for 5 to 20 minutes. The process will create *temporary* bruise marks on the area being treated. When I had it done, I found it very slightly painful.
I recommend you have it done by an experienced practitioner. If you want to try it yourself (with the assistance of a friend), there is a set of instructions in the following book: