The five koshas or bodies are the layers or sheaths of embodied experience. The goal of all yoga practices is to purify these sheaths to uncover the Atman or the Divine Self, or "unconditioned consciousness." All of our actions accumulate in the 5 koshas, known as karma, which affects future experience and perception.
Each action we take has the effect of clarifying or obscuring the divine self. You could think of it like panes of glass, there are actions which make the layers more transparent and actions which gunk up the glass so that its hard to see through.
Each of the yogic practices, cleanses or purifies one or more of these layers or bodies.
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