The word Kriya means action. But Kriya is not just any action. It is an action that leads to a complete manifestation; that makes a seed grow and blossom, makes a thought become reality, a desire becomes a commitment.
Kriya in Kundalini Yoga refers to a series of specific practices that include asanas, movements, pranayama, mudras, mantras and techniques that are integrated into a fixed sequence with the aim of manifesting a particular state. It is a specific configuration to achieve a certain objective. Thus, there are several kriyas, each for a different purpose. So, when you do a Kundalini Kriya, the result of its repetition is access and mastery of a particular, predicted and established state, as a particularity of consciousness.
In Kundalini Yoga, Kriya Shakti is the power of the soul to manifest itself in each realm of experience, the realm of mind through proper thought, the realm of the body through proper movement and form, the realm of action through the power of will of manifesting creativity to serve the infinite, etc.
You will find the word Kriya often used as Kriya yoga, Kundalini kriyas, Kriya shakti and Kriya Hatha Yoga. The Kriyas of Hatha Yoga, for example, are known as ShatKarma or Shatkriyas and are used for cleansing and purification. Kriya is also called Tattwa shakti, which is the ability of the great soul of the Universal Being to create new categories and levels of manifestation of the mind, in the body and in the world.
When you learn to act with Kriya, then actions become aligned with the larger patterns of being. We enter kriya by removing the blocks, attachments, ignorance and ego, which prevent us from acting when we should act.
Doing a Kriya is entering a state of spontaneous flow. Perfecting a kriya brings a sense of grace, power and the ability to complete things. Each Kriya is complete in itself. It is a perfectly designed set, intended to produce subtle and predictable impacts of the total Being.