Kriyas are specific sets of exercises, breathing techniques and sound mantras used to unlock energy channels or chakras in the body. The sequence of each kriya is meant to enable subtle and direct changes in the body and mind of the practitioner. Also, a kriya sequence can support a specific body part or organ, such as the intestines, liver, spinal column, etc.
Yogi Bajan, the founder of Kundalini yoga, taught each kriya in a specific sequence and these guidelines are followed by all Kundalini yoga teachers. In a Kundalini yoga class, a set of kriyas are practiced after the initial mantra chanting and warm up.