Kriya simply means method, practice, technique. Having said that, we should understand that there is no technique to find the Truth. However, you can prepare the ground from where it is possible to take off, perhaps. It is a Sadhana to prepare yourself to open your windows so that when the breeze of grace blows, you have not closed your windows and it comes in.
The aim of Kriya Yoga is to help the aspirant advance towards freedom from the constant fluctuations of a disturbed mind. Regular practice over a period of time aids in peaceful and calm meditation, and ultimately helps to naturally achieve a state of well-being and content, by discovering the source of happiness within ourselves.
Sri M was initiated into the practice of Kriya Yoga by his personal Guru Maheshwarnath Babaji, who was from the Nath Sampradaya (Tradition). His Guru was Sri Guru Babaji.
The Naths were yogis par excellence. The asanas, pranayama, kriya yoga, bandhas, and mudras were practiced and perfected by them. All the important works on yoga, like the Goraksha Shataka, the Gheranda Samhita, the Hathayoga Pradipika, and so on were written by Nath yogis.
The basic purpose of Kriya is to balance your breath. The breath (Shvasa) is closely linked to your life energy (Prana). So Kriya is the method by which the prana is balanced which is usually dissipated through the 108 nadis (channels).
Kriya is a form of rhythmic breathing, by which you can manipulate your breathing and connect it to the energy – Prana, and make it ascend to higher levels of awareness. It is a blissful experience, wherein your mind expands and becomes one pointed to touch That.
If therefore thine eye be single, thy whole body shall be full of light. (Mathew 6.22)
According to yogic anatomy and physiology, the human body or system has innumerable channels through which the energy flows. However, the important channels are the Right, the Left and the Central. The left and the right channels are called ‘Ida’ and ‘Pingala’. The energy flows through them, for any activity on this earth, including studying, learning physical activity, food, eating, sex etc.
However, to go into the interiors of your consciousness, the mind needs to be clear, free of prejudices and pre-conceived ideas and therefore open to receive. Kriya is one way to harness all the energy that is in you, which is usually dissipated and bring it to one point.
You need to gather these energies which are in the Ida and the Pingala, bring them into Mooladhara chakra, make them travel along the Sushumna, from which when the Prana or the energies begin to operate, then your awareness rises from the gross to the subtler and the subtler and finally you touch That, which cannot be understood by the five senses.
For that you need to open up other instruments of perception and some of them are placed in the central channel through which the energy travels, till it reaches the top of the head, which is the Sahasrara, the thousand petalled Lotus. This movement is the practice of Kriya – to channelize the Prana and open up the centers of perception, which takes your awareness to the higher levels, to start with.