The word kriya means action. It is an action that leads to a complete manifestation like a seed leads to a bloom, a thought into actuality, a desire to commitment.
In the practice of Kundalini Yoga, postures, also known as asanas, combine with breath, mudra, eye-focus, mantra, and body locks to affect body, mind, and soul.
The first and last things we do in this physical lifetime are to take a breath. Along with oxygen, nitrogen, and carbon dioxide, the breath contains prana, the life force.
Meditation in Kundalini Yoga contains specific, practical tools that carefully and precisely support the mind and guide the body through the use of breath, mantra, mudra, and focus.