Yoga is an activity that I engaged in for years. In the U.S. 20 years ago there were primarily a single type but over the years there have been many different types that have propped up. Some of them are fads and some of them are beneficial. Yin Yoga seems to be a pretty good new comer that allows for deeper stretching without all of the physical exertion.
It is important for people to maintain their flexibility into old age. It is also important for sports enthusiasts to stretch those hard to reach places for higher performance. That is more likely to happen with longer hold stretches. In Yin Yoga you hold your positions for over 3-5 minutes with props that don't put pressure on your body.
The advantages are significant. If you have a sore back from playing polo it can be hard to reach some of those places. Yin Yoga offers opportunities to slowly apply pressure on those spots until they have had time to stretch. Simple body pressure helps reach the stretch deeper.
There is also the additional benefit of meditation and reflection. Because it is often conducted in dim light, music, groups, etc... you can't but help let your mind start to wonder. It takes on a meditative role. I'm not that familiar with the style but you may want to check out https://yinyoga.com/. For most of us it may be beneficial to use on a regular basis.