Hatha yoga is a preparatory process of yoga. The word “ha” means sun, “ta” means moon. “Hatha” means the yoga to bring balance between the sun and the moon in you, or the Pingala and Ida in you. You can explore Hatha yoga in ways that take you beyond certain limitations, but fundamentally, it is a physical preparation – preparing the body for a higher possibility.
There are other dimensions to this, but to put it simply, just by observing the way somebody is sitting, you almost know what is happening with them. If you have observed yourself, if you are angry, you will sit one way; if you are happy, you sit another way; if you are depressed, you sit yet another way. For every different level of consciousness or mental and emotional situation that you go through, your body naturally 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 also elevate your consciousness.