Moxa is another name for the herb artemesia mugwort.  Mugwort has been medicinally used in Chinese medicine for thousands of years in a process called moxibustion.    Simply put, moxa is burned over the body to help warm it during an acupuncture treatment.  By using moxa we are able to build qi in the body and help it move easier.  This is especially useful when a patient's pain is caused by not enough qi or when there is a lot of cold in the body.