Buddhi is one of four functions of the mind; the other three being manas, citta and ahamkara. Buddhi helps to make the right choice as it is the inner wisdom.
Buddhi is attracted to Brahman, or Truth. To achieve the state of Brahman, yogic practices for purification of the soul are performed.
Buddhi yoga, also referred to as the yoga of consciousness, promotes self-development and consciousness. It helps to unite the mind with the higher Consciousness, overcome weakness of the mind, and to attain evenness of mind.