- last update 12 Oct 2019 -
Basically no difference at all although some people do use the first term to refer to Tai Chi taught for health and exercise and the second to Tai Chi taught as a martial art.
Qigong (or Chi Gung) are exercises, often of ancient origin that with only a few exceptions are taught only for health and not for martial arts purposes. Tai Chi was originally a martial art but is more generally taught nowadays for it's health and exercise benefits. So, the basic answer is that both help each other and will help you become fitter and more at ease with yourself and life in general.