The Taoist concepts of Yin Yang describe the two qualities or energies present in everything, one cannot exist without the other - they're interrelated and relative. Yin is the feminine principle and its qualities can be thought of as more internal, passive and cooling, while Yang is more external, dynamic and warming.
The class begins with a Yang practice which is dynamic and energetic, targeting the muscles and breath and improving strength, fitness, balance, tone and stamina. The class will end with Yin practice, with the purpose of surrendering, with the support of the props - bolsters, blankets, straps and blocks.
Yin yoga is deeply relaxing and nourishing, designed to target deep connective tissue (by application of long, slow deep holds) and therefore aides healing by stimulation of the nadis / meridians which ultimately loosen energetic blockages and increase energy flow to the regions upon which are worked on.