Yin / Yang : Two halves that together complete wholeness. Yin and yang are also the starting point for change. When something is whole, by definition it is unchanging and complete. This starts both halves following after each other as they seek a new balance with each other.
The word Yin comes out to mean “shady side” and Yang “sunny side”.
Yin Yang is the concept of duality forming a whole. We encounter examples of Yin and Yang every day. As examples: night (Yin) and day (Yang), female (Yin) and male (Yang). Yin/Yang energy are both equally important aspects of the whole. Without understanding negative, one can not understand positive, or female without male. Two opposite aspects must be balanced in Yin and Yang to function properly because they drive each other. Yin and Yang is a philosophy not about making a judgement of which is better or worse, but about achieving balance and harmony.
There is no absolute Yin or Yang; this is why the Yin/ Yang symbol is shown containing a portion of each other. A black circle inside the white and a white circle inside the black illustrated that all Yin contains some Yang and vice versa.