This Yang-Yin symbol is of Chinese origin, and is more than three thousand years old. It represents the unity created by a balance between two opposing forces that are equal and contrary.
By Bruno Munari in his book Design as Art
This unity is visibly represented by a disc made up of two equal parts, one black and one white. These parts seem to be in constant movement in a clockwise direction.
The two opposing forces are interpreted as natural forces, and from their balance comes life itself.
Yang is the positive, active, masculine force, and subsists in dryness, heat, hard-ness, the sky, light, the sun, fire. It is firmness and bright-ness.
Yin is the negative feminine principle present in everything passive, such as cold, damp, softness, mystery. It is in all mysterious, secret, evanescent, cloudy things, and in everything inactive.
The shadow on the north side of a hill, the estuary of a river, earth and water: these are Yin.
The same goes in business. Profit and loss, success and failure, growth and downfall go hand in hand.