When you are practising asana, understand the changes that happen in your body, mind and senses at the gross level, subtle level, causal level and supreme level.
There are millions of asanas. It is not possible to know all of them. Neither one can practice all those asanas.
In certain asanas, after reaching the physical position of the asana, the mind begins to focus on the asana according to the name and subtle meaning of the asana. In these asanas, the physical work is limited and confined. The mental practice is deep and focussed.