The Chakras are subtle energy centers found in the subtle body, also known as the psychic body, but there are correspondences for their action in the gross physical body. For most people the corresponding physical centres of energy are closed and they do not have immediate, complete and direct access to the force that is available to them when the chakras open. Yogic practices, however, can open these chakras, move the energy from the lowest center to the highest and awaken the practitioner into a state of superconscious awareness in Samadhi.
Sri Aurobindo describes this process briefly: “These Chakras or lotuses, however, are in physical man closed or only partly open, with the consequence that only such powers and only so much of them are active in him as are sufficient for his ordinary physical life, and so much mind and soul only is at play as will accord with its needs….The whole energy of the soul is not at play in the physical body and life, the secret powers of mind are not awake in it, the bodily and nervous energies predominate. But all the while the supreme energy is there, asleep; it is said to be coiled up and slumbering like a snake,–therefore it is called the kundalini sakti,–in the lowest of the Chakras, in the muladhara. When by Pranayama the division between the upper and lower Prana currents in the body is dissolved, this Kundalini is struck and awakened, it uncoils itself and begins to rise upward like a fiery serpent breaking open each lotus as it ascents until the Shakti meets the Purusha in the brahmarandhra in a deep Samadhi if union.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 28, Rajayoga, pp. 515-516