The Yin-Yang Theory in Feng Shui

The Yin-Yang Theory in Feng Shui   From Rodika Tchi,

The Yin Yang Theory is one of the main theories of feng shui. According to it, everything in the universe consist of two opposing, but deeply interconnected forces - Yin (feminine) and Yang (masculine) The movement and interplay of these two forces create all life around us.
Here is how to understand, or relate to this interplay on a practical, day to day level.
YIN (passive energy) is often taking form as silence, deep darkness, slow movements. It is the predominant energy at night when you go to sleep, or when you need to relax and replenish your energies.

YANG (active energy) is the one that manifests itself when you are active, and is characterized by loud sounds, bright lights, upward moving energy, etc; it is the energy you experience in a busy office, at a great party, or driving on the highway.
One cannot exist without the other, just like day will not be day without the night; sound without the silence that precedes it, and hot temperature without the cold. They cannot exist in isolation; one is the condition for the other's existence.
The best representation of the interaction of Yin (Black) and Yang (White) is the Tai Chi symbol: a perfect circle harmoniously created by two parts, black and white, flowing together and each containing inside itself a dot of the color, or the essence, of the opposite sign.