Tai Chi is essentially a martial art yet its intrinsic nature is non-aggressive. Its foundations lie in an integration of many Chinese cultural influences: several ancient philosophies of self-cultivation (encompassing individual, social, spiritual and environmental perspectives) as well as martial practise and Chinese medicine, for example.
The popular story that a monk called Zhang Sanfeng was delivered Tai Chi in a dream is a mythical tale, even if it is a great story.
All forms of Tai Chi Chuan taught today can be traced back to Chen-style and its origins in the Chen village between about 1600-1680. The originator of the art was a warrior and scholar, Chen Wangting. Chen-style Tai Chi Chuan has since been passed down through the generations. The 19th Generation Lineage Holder is Grandmaster Chen Xiaowang.
Tai Chi Chuan is a soft, or internal, martial art. It doesn't rely on brute strength and power to be effective. It relies on refined knowledge and cultivation of the alignment, co-ordination, and subtle workings of the mind and body. This is what makes Tai Chi so ideal as a system for promoting health and wellbeing, which is what most people practise Tai Chi for nowadays. I also emphasise the health and wellbeing aspects in my classes (but without forgetting its complete heritage).