Yin yoga and the body
While Yang yoga practices (Ashtanga, Vinyasa) physically target the 'superficial' muscles, in Yin yoga, we target the deep connective tissues of the body - the ligaments, joints, bones, and deep fascia networks. A Yin class usually consists of a series of passive floor poses held for up to 5 minutes or more, that mainly work the lower part of the body - the hips, pelvis, inner thighs, lower spine. These areas are especially rich in connective tissues.
On an energetic level, Yin yoga improves energy flow and enhances the flow of chi in the organs but the practice also offers huge mental and emotional benefits too, as we'll find out.
Yin yoga and the mind
Becoming still in a pose and staying for a while creates those gaps that I referred to earlier. Keeping the gaps empty creates space for anything that wants to come up. This could be anxiety, happiness sadness, boredom...any emotion or feeling you suppress with all busyness in your life. Yin yoga gives you the time and space to allow emotions, thoughts and feelings you have kept in the shadows, to surface.
Generally speaking, during a Yin yoga class, you will be encouraged to allow all those feelings to be there, but not to identify with them. To observe but not get caught up in them. It costs the body a lot of energy to keep things suppressed, so the release you feel from letting it all come out can be just as big.