"Tai Chi" can be translated as the "Supreme Ultimate". The notion of 'supreme ultimate' is often associated with the Chinese concept of yin-yang, the notion that one can see a dynamic duality (male/female, active/passive, dark/light, forceful/yielding, etc.) in all things.

Tai Chi, as it is practiced in the west today, can perhaps best be thought of as a moving form of yoga and meditation combined. Many of these movements are originally derived from the martial arts, although today they are performed slowly and gracefully with smooth and even transitions between each movement.

One aim of Tai Chi is to foster a calm and tranquil mind. Additionally, Tai Chi helps to improve balance, alignment, fine-scale motor control, rhythm of movement, the genesis of movement from the body's vital center, and so on. Many practitioners notice benefits in terms of correcting poor postural, alignment or movement patterns which can contribute to tension or injury. Furthermore the meditative nature of the exercises is calming and relaxing in and of itself.

Abridged from http://www.chebucto.ns.ca/Philosophy/Taichi/index.html