The origin of the word Yin Yoga is deeply rooted in both the Chinese Taoist system (Yin) and the India Tantric system (Yoga). Yin Yoga is a fusion of both.
Yin Yoga is a perfect complement to the dynamic and muscular (yang) styles of yoga (such as Bikram and Hot Flow) that emphasise internal heat, and the lengthening and contracting of our muscles. It is restorative in nature (not to be confused with easy) and focuses on the deep stretching and long holds from 1-5 minutes with slower movements between. Done primarily from the floor, it targets the deep connective tissue of the body and fascia and gently joint and ligament stress with a large emphasis on the hips, sacrum and spine. This practise aims to correct postural imbalances created by tight fascia and is a stepping stone to meditation. It is a simple, quiet meditative practise, which allows the cultivation of mindfulness, inward focus and surrender.
This style is an important practise, as it accesses deep stale energy stored in the body that over time has become stagnant due to the immobility of joints. It is suitable for almost all levels of students. You need to experience Yin Yoga to really know what it is all about. After you have experienced it, even just one, you will realise that you have been doing only half of the asana practice.