Tai Chi is an exercise, yes. Tai Chi has many benefits, yes. Tai Chi is much more important than these two things however. Tai Chi is a game. It is the game of getting to know your mind and body and relaxing into who and what you are. In Tai Chi we first learn drills and movements and those are good useful things but we go beyond those things after a bit and begin using the mind to influence the physical attributes and perceptions of the body.
This is where the cool stuff starts to happen. How can you receive a larger person's full bodyweight and not be knocked over? How can you explode energy outward and throw someone with extremely little effort? How can you learn to meet an attack whether emotional, mental, or physical with total relaxation and security in the fact that you will be safe? How can you learn to trust your body to do what needs to be done at the appropriate time without micromanagement?
The answer to all of these questions lies in learning genuine Tai Chi from a good teacher. There is nothing mystical about these skills. They are a part of every single human being. We don't need to fight but we do need to learn the martial tricks of Tai Chi in order to foster a better relationship with our minds and bodies. Meditation and yoga are fine tools for this purpose as well but because I am often quite skeptical Tai Chi worked better for me because there is an automatic feedback device. Need to know if a posture is correct? Have a partner push on you. Are you really relaxed? Play some push hands. These things provide reality checks beyond just our internal feelings and they are also a tremendous part of the game. So come on let's play.