If you are learning Tai Chi, ask yourself "what is it all about", and keep asking yourself and your teacher.
The True answer is .... read on ....
There is little doubt that it was/is a martial art, and from this a holistic health system emerged, which is mostly taught today. However some use it as a martial art, some use it as a meditative 'dance' and art form, and some as a health system. The truth is that it is all of these, and more.
It should depend on what you, the student/practitioner are looking for, although (hopefully), this may change with time.
The style of Tai chi and even the moves themselves, should be secondary to the above.
So when you start it's a good idea to try a few teachers, to see which you enjoy the most.
Officially there are only 5 styles of Tai Chi, but really there are as many styles as there are teachers.