Kundalini Kriya Yoga is an ancient yogic practice for spiritual evolution and growth. It's called the lightning path to self realisation by Yogiraj Siddhanath a living Satguru and the aeroplane path by Paramahamsa Yogananda in his book Autobiography of a Yogi. The practice includes chakra purification and activation, Kundalini Pranayam a subtle and superior breathing technique leading one to a samadhi like state of Paravastha.
It is part of the Raj Yoga technique and takes one to the higher stages of yog sadhana to pratyahar, dharana, dhyan and samadhi.