Samadhi in Hinduism, Jainism, Sikhism and all yogic traditions, including Kriya Yoga, is a higher level of meditation which transcends the realms of body, mind and intellect, and where the logical and analytical ability becomes silent. That does not mean that one loses the ability to be rational. On the contrary, the state of Samadhi is a completely balanced state of being.
Once a person passes through the other 7 stages of yoga and enters Samadhi, that person is no longer a student. That person is considered an initiate.
The yogi is a scientist ever studying the mystery. Simply put, the mystery is the most important purpose of existence - to understand life. Understanding life we recognize that we all live in a heaven or hell of our own making. The purpose of the practice of yoga is to attain a state of bliss. To understand that this day, this moment is part of your/our immortality.
You are the result of all you have thought. I am the result of all that I have thought. The Universe supports every thought you/I/we choose to think and believe. When we practice living in the world in a balanced, feeling state, we naturally move toward that which is harmonious and peaceful. Surface perception does not reveal the true nature of the mind which is why, in yoga, we practice repeatedly to attain a deeper meditation, a deeper level of Samadhi.
Samadhi is a soft, tranquil passivity which burns up our craving for things. In Samadhi you break the false attachment of "I" and come to understand that "I" is pure consciousness. This leads to unselfish love which is the ultimate discipline of yoga. Samadhi is not dependent on externals. To the lover, the World is the beloved. Love without grasping. And Truth is something that no one can give to you and no one can take away from you. It has no beginning and no end. It is always there. Waiting to be discovered.
Shanti, Prem and Namaste,
S.