That is a very important question because for most of us, practice is done through the body and externally it may look very much like gymnastics. Hence, many people think that yoga practice is done for fitness: to get a better body, to be stronger or to become more flexible. Yoga, however, is not at all about this! Asana practice will definitely do well for your body, but this is just a byproduct and not the aim (See the chapter “The aim and the by-product” in Tree of Yoga by B.K.S. Iyengar).
read more: Why do we practice yoga? by Eyal Shifroni