Yin yoga is rooted in the tradition of of yoga and Taoism and utilises Ancient Chinese Medicine, whilst it it also uses the findings of modern (Western) medical science. It is a quiet practice, a slow, meditative style of yoga. It consists of long-held poses, mainly sitting or lying on the mat. It is a gentle exercise that is completely appropriate to anyone, independent of age, experience, gender or "flexibility".
YIN yoga is a perfect counterbalance to the dominance of YANG (achievement, activity, competition, speed) in modern life. It is a complete practice for body and mind.