Describing what happens in Yoga
Here are a couple ways of understanding what might happen in yoga, from a philosophical perspective.
The most discussed explanation is the whole idea of steadying the fluctuations of the mind (called vrittis in Sanskrit). If you’ve been going to yoga classes, you’ve probably heard the teacher say or read something like this: we are surrounded by distractions that take us away from our true self. Yoga is a technique that allows us to not be pulled this way and that (by both negative and positive circumstances and their effects on us). Sometimes I think this describes my experience, especially when in sitting meditation, but then it doesn’t fully account for what happens during yoga practice.
There is also another concept, not as examined as the above, that describes the practice as more of an absorption into the universe (or divinity) called prakriti-laya in Sanskrit. This also makes sense to me, especially when in the flow of asanas practice.
Many more concepts and explanations exist, the work of philosophers and practitioners, great teachers and sages from different traditions. Ultimately they all point to the need to experience it through your own practice. Articulating what happens then begins a whole other process, partly intellectual, frequently artistic as it takes the form of ecstatic poetry or precise sutras.