The four higher planes are eternally pre-existent, and constitute the modes or qualities of the Absolute (in Indian philosophy, the Absolute is described as being Sat-Chit-Ananda or Sachchidananda, of the nature of pure Being, Consciousness, and Bliss. The Supermind is Sachchidananda in manifestation; the transitional stage between the unchanging planes of Sat, Chit-Tapas and Ananda and the finite lower ones. Aurobindo considers it pivotal for the Divine transformation of the world. "It alone contains the self-determining Truth of the Divine Consciousness (that) is necessary for a Truth-creation." [Letters on Yoga, vol 1, p.239]
Between the Supermind and the lower three planes is a transitional level, the Overmind, a level of global or cosmic consciousness. Beneath the Overmind one passes from Truth (albeit a multiform, rather than as in the Supermind a Unitary, Truth) into falsehood and ignorance. These are the lower planes of Mind, Life, and Matter. It is also in these lower planes that their dwells the Divine Soul, or "Psychic Being".
The terminology in all this is a little confusing, for Aurobindo and Mirra use the term Life or "Vital" to designate what Western occultists and Theosophists call the Astral plane. "Vital" in this context therefore has nothing to do with the life-principle (the Etheric plane of Steiner and the Prana of the Hindus). Similarily, "Psychic" is used to refer to the Spiritual or Higher Self, the Divine Soul, rather than the Astral realms, as is the case with the common understanding of the word (e.g. "psychic experiences"). This curious terminology derives originally from Max Theon, Mirra's teacher in occultism Kheper Home