(in Chinese philosophy) the passive female principle of the universe, characterised as female and sustaining and associated with earth, dark and cold.
For many a yoga practitioner alike, sometimes our motivations for attending class can easily fall down the misguided rabbit hole of over-exertion, over-strain and over-striving for an aesthetic outcome of how a pose should look; rather than feel. Whilst steadily training for an intermediate or advanced posture is indefatigably rewarding at the point of accomplishment, sometimes we get a little too egotistically indulgent about the out-come along the way.
Yin yoga is the antidote to the qualms of a surface driven approach to wellbeing and exercise. Yin yoga asks you to close your eyes. The practise evangelises deep listening, asking: "Where can I find less gripping and more softness? How can I better encourage my body and mind to unwind? How can I consciously do less with both my body and my mind? Can I be quiet enough to listen to the silence within me?”
The actual effort involved in Yin yoga is the willingness to look at how and where we hold tension and in turn consciously allowing more breath, more prana, to flood these target areas with revivified energy and compassion. Discovering how and where we hold tension, by practising deep listening, allows us to inspire change so that neither mental nor physical tension can limit any aspect of our wellbeing.
During a Yin yoga practise, the muscles are kept soft and you adopt a long-hold approach to asana. By keeping your muscles soft, deep layers of tension are released within the fascial network of muscle connective tissue – this remedies tightness like no other trick-in-the-book. Not to mention, on an energetic level, in this way Yin enhances the flow of prana (life force) into the tissues around the joints (where energy often stagnates), which provokes better joint function and thus better bodily function and mobility all round.
And then there are the mental benefits: Yin yoga revolutionises your life from the inside out. Holding poses for three to eight minutes often unearths a lot of mental turf. But in-amongst this internal muddle, Yin yoga asks you to allow yourself to deeply ask, again: “where can I find less gripping and more softness?” - This compassionate approach to deep internal listening triggers a self-righteous initiative response within, demanding: “What am I doing to disturb my own health and wellbeing, and what can I do about this?” As you practise responding to yourself in this manner, with kindness and curiosity rather than judgment, your nervous system actually shifts from the stress response to the relaxation response, which - not only calms muscular tension as we discussed above but also – sets-up your entire ecosystem for deep healing, growth, repair and allows you to access your inner wisdom. 
Yin yoga’s no-pressure approach conditions you to stay with the intensities within, rather than quickly moving into the next pose. It guides you to become more tolerant of mild discomfort, rather becoming alarmed or overwhelmed. This is the heart of deep listening and where the alchemy occurs in Yin yoga, with regards to tackling habitual tension.
Whether your habitual tension may be bodily, or within the narratives whirling around in your head, Yin yoga creates the conditions for us to cultivate the skill of conscious relaxation. No matter how you incorporate Yin, you will find yourself better able to be quiet and listen to your body and your thoughts without judgment, shame, or criticism. You'll begin to know which parts of your body need extra care and attention. You'll be able to tune into your emotional world and kindly nurture your vulnerabilities and insecurities from a meditative approach. With all this knowledge, you will be able to construct a practise that negates the importance of how you should look on the outside, and prioritises the importance of how you feel on the inside.

Interested in learning a little more about harnessing the powers of mindful breathing? Check out this post on Pranayama