Yoga is not an exercise form as is commonly misunderstood today. “Yoga” literally means union. Modern science proves that the whole existence is just one energy – but you are not experiencing it that way. If you can break this illusion that you are separate, and experience the oneness of existence, that is yoga. To lead you towards this experience, there are various methods. Asanas are one aspect.
There are other dimensions to this, but to put it simply, if you observe yourself, when you are angry, you sit one way. If you are happy, you sit another way. If you are depressed, another way. For every level of consciousness or mental and emotional situation you go through, your body tends to take certain postures. The converse of this is the science of asanas. If you consciously get your body into different postures, you can elevate your consciousness. Understanding the mechanics of the body, creating a certain atmosphere, and using the body to drive your energy in specific directions is what yogasanas are about.