Tai chi chuan is an internal Chinese martial art often practiced for a variety of reasons including health problems: its soft martial techniques, demonstration competitions, health and longevity. Consequently, a multitude of training forms exist, both traditional and modern, which correspond to those aims. Some of tai chi chuan's training forms are well known to Westerners as the slow motion routines that groups of people practice together every morning in parks around the world, particularly in China.
The name "tai chi chuan" is held to be derived from the Taiji symbol (taijitu or t'ai chi t'u), more commonly known in the West as the "yin-yang" symbol. Tai chi chuan is therefore said in literature preserved in its oldest schools to be a study of yin (receptive) and yang (active) principles, using terminology found in the Chinese classics, especially the Book of Changes and the Tao Te Ching.