The taiji symbol of yin-yang, light becomes dark and darkness becomes light. Taiji movement expresses these relationships.
Taijiquan is much more than doing the form. Form is the culmination of several practices. It’s the frame into which you unite them into a collective activity—breath, central equilibrium, gravity, connected movement on the outside, flowing on the inside, intention guiding it all. So if you learn a breathing technique, for example, then be sure to incorporate it into your practice.
Tai chi is a way to open up your awareness to these things that make up the whole being. We are complex and tai chi is a way of navigating the complexity. It frames out an approach to learning. Built into the movements themselves are signs for how to learn them.
That has to do as far as I can tell, with focusing the attention, and focusing it on one thing at a time, at least in the beginning—in the beginning of practice over period of time and every time you stand in wuqi and begin a practice session.
What is meant by “attention”? I can’t say entirely, but I do think our senses make up its components. Tai chi is a way of using our senses, improving them and how we use them, helping them to function better. From this viewpoint it’s easy to see how we could open ourselves up to endless discovery.