Yin and Yang 
     A dualistic philosophy of passive and active, good and bad, light and dark, positive and negative, male and female, etc., and that they are in opposition, each is part of the whole and works together.

Yoga
     A philosophical as well as physical way of life emphasizing harmony of body and mind.  The philosophy of yoga is based in Eastern Metaphysical beliefs.  The goal of the philosophy is to help a person become balanced in mind and body and attain self-enlightenment.  Yoga, apart from its metaphysical teachings, is beneficial to the body.