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 usually characterized as slow, soft, insubstantial, diffuse, cold, wet, and tranquil. It is generally associated with the feminine, birth and generation, and with the night.
Yang, by contrast, is characterized as hard, fast, solid, dry, focused, hot, and aggressive. It is associated with masculinity and daytime
The principles of yin and yang and the five elements complement each other. Each element has a yin and a yang character, which makes quite a difference energetically. Generally you can assume, that the element in his yang character is always stronger and more active than the softer yin variation.