Definition - What does Yin mean?
Yin is part of the Taoist concept of the balanced and harmonized energies in nature, with the other part being yin's opposite: yang. The characteristics of yin include slow, gentle, female, passive, dark, mysterious, earthy and internal. Yogis may wish to practice Yin yoga in order to harness these particular qualities found in yin’s energy.
Yogapedia explains Yin
In Taoist philosophy, Yin/Yang is the idea that the two energies found in nature come together to form a balanced whole. This concept is mirrored in the opposites of night and day, male and female, and water and fire.
Yin yoga is based on principles from both India's Hatha yoga and China's Taoist philosophy and practice. It was established in the Western parts of the world by Paulie Zink in the 1970s.
Yin yoga seeks to cultivate the characteristics of yin energy: night, moon, female, water, among others. It is a slow-paced and gentle form of yoga that is paired with mindful meditation incorporated throughout the practice of the asanas. Yin yoga practitioners seek to nurture silence within the self and interconnectivity of the self with all things.