The classical account gives four functions: warming the channels and dispersing cold, supporting yang and preventing collapse, resolving stasis and dissipating nodules, and preventing disease. The first two are the most used and the best supported.
Mechanically, moxibustion delivers radiant heat and infrared radiation to a small area, together with the combustion products of the herb. Modern study has looked at local circulation, at immune markers and at the thermal response of the viscera, and finds measurable effects without a settled explanation. The traditional account remains the more useful guide to when to use it: cold, deficiency, and chronicity.