Yin-Yang or Yin and Yang are concepts in Chinese philosophy that are usually used to describe the nature of the interconnected and opposing forces in this world and how they build on one another. The concept is based on the origins of the many branches of classical science and Chinese philosophy and can be used as a guide to Chinese medicine and become a principle of martial arts in China, for example Baguazhang.

~ Yin ~
Cold and weak nature (Cont: Woman, night, water or wind etc.)
~ Yang ~ hot and strong (cont: Men, heat, fire, etc.)
Yin and Yang are always the opposite, but their application in life must be balanced. If not, it will cause disharmony in life.
The Yin Yang symbol is two black and white fish in a circle. This symbol is called the Xiantian Taiji or Yinying Coat which was popularized by Lai Zhide (1525-1604M).