Yin is the black side with the white dot on it and yang is the white side with the black dot on it. The relationship between yin and yang is often described in terms of sunlight playing over a mountain and in the valley. Yin (literally the 'shady place' or 'north slope') is the dark area occluded by the mountain's bulk, while yang (literally the 'sunny place' or 'south slope') is the brightly lit portion. As the sun moves across the sky, yin and yang gradually trade places with each other, revealing what was obscured and obscuring what was revealed.

Yin is characterized as slow, soft, yielding, diffuse, cold, wet, and passive; and is associated with water, earth, the moon, femininity and nighttime.

Yang, by contrast, is fast, hard, solid, focused, hot, dry, and aggressive; and is associated with fire, sky, the sun, masculinity  and daytime.