5000 years in the making
Qigong [‘tsjee-kung’] is a holistic system of self-healing and meditative exercises that anyone of any age can do. You don't need a marathon-condition or expensive shoes to practice. And you definitely don't need to be wearing funny clothes. Qigong works with what is always there inside of you: energy. To free and allow it to flow. To free who you are.
Qigong goes back 5000 years and has been elevated to an integral part of Chinese medicine. I think that's a really good idea, because Qigong is about much more than "just" health. As is Tai Chi.
Tai Chi [‘tai-chee’] is a 400-year old discipline traditionally practiced as a martial art. Tai Chi guides the forces that are naturally present within us to a state of balance and centeredness. Tai Chi will not teach you to fight like a man (whatever that means). It will make you conscious of how you use your energy. It will teach you to focus that energy and keep it flowing, making for a direct (positive) influence on your vitality and health.
And so, the difference between the two... A short investigation shows Tai Chi mainly as a type of Qigong, or as different to but very closely related to Qigong. That doesn't really tell us much of course. But it's nice to know that Qigong enormously helps in practicing and understanding Tai Chi. And you will find many Tai Chi movements in the practice of Qigong. Together they are more than the sum of their parts.