Chi Kung is an ancient Chinese discipline for the cultivation of health through mastery of Chi, the internal energy essential to both Chinese medical theory and to all life. While the Tai Chi and Qi Gong have much in common, they are distinct practices with distinct applications.
"Ch'i" or "Qi" is the Chinese word for breath, energy, vital force, air, or life power; and, there are different types of Ch'i. The Sanskrit word 'Prana' and the Japanese word 'Ki' are very similar in meaning to 'Qi.'
The word "Kung" or "Gong" implies a regular, systematic, intense, long term, and dedicated training regiment.
Therefore, "Ch'i Kung" or "Qigong" is a long term training program to circulate, cultivate, regulate, enhance, and guide vital internal energies to achieve health, vitality, and spiritual awareness.
Before the 1940s and 1950s, qigong was practiced in a multiple of ways, and sometimes referred to as "Dao-yin." The Chinese government regularised it and used it as a health practice in hospitals and state run facilities. After the Cultural Revolution it became widespread for Chinese people to practice forms daily, to enhance their health.
Qigong forms are different from Tai Chi ones in that the movements are less circular and can be quite angular at times, but both are performed slowly and both benefit health by channelling Chi by using Yi.
Don't start any exercise or fitness program without carefully assessing your state of health and level of physical conditioning, and consulting with your personal physician when and where appropriate.