Tai chi is many things and one way to answer the question of what tai chi is to see it as a quest to understand two things. One—that Qi (life force, energy of life) moves. It moves all by itself. “Qi flows through,” the master says. It flows through everything, everywhere. It is life force. If it is not flowing, it’s because something is stopping it. Often it’s an injury, but more often, it’s simple tension in our bodies. Often, we don’t recognize that it’s not flowing; that it’s stuck. It could be from an injury, an acute condition. Or it could be a chronic condition that refuses to go away on its own. If you understand this, you have greater capability to change it for the better. Tai Chi practice is an effort to recognize this. Once you recognize tension you can do something about it.
Two—Qi, once it is freed up and moving, can be directed. You can visualize or intend it to go where you want; for example, to a part of your body that needs healing. As a beginner, this may be better understood by releasing tension in such a way that it flows freely. It will flow on its own without your help. With this you may direct it to wherever you want. So practice is an effort to recognize tension and using your mind intention to release it.
“What is qi?” you may ask. It’s a feeling that changes. That change is yin-yang. It’s separation and movement. What makes the wind blow are changes in air temperature. Hot and cold air masses collide either slowly or quickly and air is compelled to move. Hot rises, cold descends, like the yin-yang symbol (taiji tu). Cold air rushes in and hot makes way. You can do something similarly with your powers of intention and visualization. Put it into practice.