Hatha yoga is a style of yoga founded by Lord Shiva that focuses on balancing the sun (Ha) and moon (Tha) nadis or energy channels. It aims to bring harmony between the sympathetic nervous system associated with the sun and right side, and the parasympathetic nervous system linked to the moon and left side. Key aspects of Hatha yoga include holding poses for longer periods to improve alignment using controlled breathing that requires willpower and develops strength and flexibility of both body and mind.