Tai Chi is a dance.
It is a sequence of slow movements which is dedicated to build the physical and spiritual aspect of your body. It is a dance but you do not need music to dance it. You just need to look inside and listen to the rhythm of your inner nature.
It was created thousands of years ago as a marshal art and specifically as a defensive technique. However its marshal aspect nowadays is not that popular. It is practiced by thousands of people around the world mostly because of its miraculous effects on humans health.
It is often called meditation in motion because it combines the bodys movements with the calm and meditative state of mind.
TaiChi is a possible way of practicing Qigong. It is often referred to as meditation in motion because it combines the bodys movements with the calm and meditative state of mind.
Qigong on the other hand is usually associated with meditation and in practice is moving the internal bio energy in the different channels of the body. Thus qigong is not associated with a physical movement. The movement remains hidden and inner. For a person who is not versed in the specifics of qigong somebody practicing will seem remaining in stillness for hours. However there is motion in qigong. The person is just working with and focusing on the inner movements such as the energy movements in the channels, blood movements in the vessels, cyclic movements caused by breathing. Thus qigong combines both stillness and motion although motion is not easily seen by ordinary people.
TaiChi combines stillness and motion as well. Its core is to maintain in harmony the rhythmic physical movements of the body and the stillness of mind.
Stress is usually associated with misbalancing the internal self regulating mechanisms of the body. Stress is dedicated to bring the body in a state to perform more intensively than normal in order to save your life or find out the solution of a problem.
However this state should be temporary. If it lasts for long it becomes detrimental to all internal processes of the body.
TaiChi is a very good technique to restore your inner balance and as such becomes indispensable technique for stress relief.