Qi (pronounced chee) is the Chinese character for air, breath, life force, or life-essence.

Gong is the character for effort, work, and labour.

Thus Qi Gong, sometimes spelled Chi Kung, essentially translates into `the work of strengthening one's life energy".

People often mistake Tai Chi and Qi Gong as one and the same thing, however Tai Chi is a Martial Art. The form, Pushing hands, the weapons forms etc, all relate to this aspect of the art. There are many types of Qi Gong , Daoist, Buddhist, Medical and Martial to name but a few of the major styles.

Qi Gong is a series of breathing and physical exercises that people of all ages and physical conditions can easily perform. Qi Gong requires no special equipment, time, or place.  It requires as much or as little time as you can dedicate daily, spent in a concentrated state of mind, performing a set of simple - yet powerful - mind/body/spirit exercises (static, moving and meditative) to bring the person together as a whole.

The goals of Qi Gong exercise are to promote self-healing, maintain good health, and to build internal strength, fitness, and balance.  By learning and practicing a set of concentrative techniques, controlled breathing techniques, and specific slow movements or postures, Qi Gong practitioners can circulate, control, and cultivate the Qi that flows through the energy meridians within the body.  This Qi then nourishes and strengthens the body and when property cultivated and stored, may be used in healing others.  People who practice Qi Gong feel calmer, more energized.  They also look remarkably "well".

When the body is relaxed, Qi starts to grow in the Tan tien (Dan Tien), then moves to the legs and the feet. When the legs are strong, the back will also become strong. More practice builds up the Qi in the tan tien, more Qi makes you stronger. However developing the Qi can take a little time. When the body movements are correct, the body is relaxed and the Qi can develop.

One of the goals of practicing qi gong is to make our qi circulate strongly through the meridians in our bodies. This helps us resist or overcome imbalances or blockages and their resulting disharmonies. That is also the goal of acupuncture and Chinese herbal medicine. Qigong therefore 'fits' into the regimen of Chinese medicine. The qi gong art thus plays a fully active role to prevent disease or permit recovery.

Chinese herbology, acupuncture, and qi gong are three parts of a single entity, as closely related as water, steam, and ice. They can be and often are used separately, and may be used together. With dietetics and massage they are considered to be the indispensable components of traditional Chinese health care. While acupuncture, herbal medicine and medical qi gong typically focus on curing sickness, normal qi gong focuses on maintaining good health.

Terminology

Jing
The character for jing carries the meaning of sperm or essences; Jing is considered the source of life, that forms the foundation for growth, reproduction, and development. Jing is responsible for bone growth in children, teeth, hair, normal mental development and sexual maturity. After puberty, jing engenders reproductive function and fertility. Deterioration of jing can be accelerated by prolonged illness or overwork, injury, abuse, stress, exhaustion, excessive sex, and poor nutrition. Evidences of jing waning are thinning and graying hair, decreasing moisture throughout the body, loss of sensory and mental acuity, and weakening of the bones, teeth, and connective tissue. Chinese believed that everyone is born with a finite amount of Jing. As we go through life, we lose or consume our Jing little by little. Once we lose Jing, it cannot be replaced. It is gone for ever. But Jing can be preserved if we live in moderation. The rate of deterioration can be slowed down by qigong practices, and techniques such as acupuncture, and herbs for enhancing the life force.

Qi
Qi is your life force, your energy. It is vital for without Qi you would be dead for there would be no life in you. Most people gather Qi without even knowing it; they gather it from the foods they eat and by sleeping. Others have discovered how to gather more Qi through meditation, martial arts like Tai Chi (Taiji), Qi Gong (Chi Kung), and through deep rhythmic breathing from the stomach. If one has a vast amount of Qi he will live longer than others who have not gathered extra Qi. Daoists believed through meditation and Qi training one could become immortal. There are even legends of venerable Tai Chi masters being able to fly because of this amazing energy.

Shen
Shen is not an automatic given to all who live and breathe like jing and qi are. It is achieved in the higher levels of taiji and qigong practice and through a lifestyle that is integral to these practices. Shen is spirit and it is everywhere. It comes to us when we reach a higher level in our practices after much time and perseverance; it goes elsewhere when we neglect our practices.  The character for shen contains the idea of a bird. A bird is free to fly away. It is free to go when conditions aren't favourable and may choose to remain when they are. We all have the capability through cultivation to have the kind of roost that the shen will be attracted to.
Diagnostically, in Chinese medicine the signs for the quality of the shen are observed in the eyes primarily and to a lesser extent skin and hair. When the shen is happy, we radiate and our eyes sparkle and mirror our souls. In serious mental illness, there is almost always shen disturbance. The sign for this is revealed by how the person looks out into the world, the gaze, how it connects (or doesn't) with the eyes of others.

Yi
Yi is intention. Your will. You use Yi everyday to talk to eat as well as to use Qi. If one has a weak Yi, Jing and Qi will be weak for they cannot use Yi to direct the transformation process of Jing into Qi, Qi into Shen.

In summery

The production of Jing depends on the action of qi while the production of qi is expressive of shen hence the need to exercise qi and transform it into shen. Movement is Jing (liquid energy) supported by Qi (essential energy) led by Yi (intent energy) created by Shen (spirit energy) . Qigong is in essence an exercise of jing, qi, yi and shen, which form the material basis for Qigong exercise and are the basic things sought after in Qigong practice. Jing, qi and shen are the very objects to be achieved in Qigong practice, the aim of which is to gather jing, nourish qi strengthen yi and preserve shen all contributing to good health.

A SIMPLE BREATHING EXERCISE

We start moving Qi first by breathing exercises and then move onto slow deliberate postures.
The picture below shows the one breath cycle of breathing or Small Heavenly Circle Qi movement.  Start by guiding the breath from the tailbone C, up the spine through the Bai Hui, B,  point to the point just below the nose D, then down  passing through the Dan Tien, E,  and Hui Yin, A, points.