The Chinese believe that there are two principle forces of nature, the Yin and the Yang. They represent all what is opposite in the universe, and all elements in the universe possess both yin and yang. The Yang is all that is positive and masculine (the white or red in the symbol). The Yin is all that is negative and feminine.
Each of these opposites are constantly in flux: sun and rain, creation and death, light and dark, wealth and poverty, power and submission. When one is stronger than the other, disharmony results. However, one principle does not dominate forever and will change to its opposite.
Every movement in the universe gives rise to a reciprocal movement. Only when the yin and yang are in harmony can Man overcome his limitations.