The astral and mental bodies are part of our spiritual bodies. In sanskrit mano means mind stuff and vijnana means intelligence. These two bodies are fused together like the physical and pranic body. These bodies are the source of our thoughts and the intellect.
Our mental abilities (including memory), personality and ego are developed in these bodies. These bodies give us the ability to create attachments to people, things and places. We absorb knowledge through the spoken or written word and formulate our opinions based on our experiences or other people's thoughts.
Our memories are stored here. Human ingenuity is born of these bodies, so also is our sense of timing and sense of purpose in life. While our physical body is the vehicle through which we express our life, it is through our astral and mental bodies that we develop the many attributes of our personality.
The astral body (manomayakosha) is the seat of our personality that drives our lives. Depending on our personal spiritual evolution, the faculties in our astral body and it’s intellectual abilities can be used either to live a life driven by baser instincts or by our divine, soul nature or a by a mix of the two. The emotions that we feel are first stimulated in our astral body before they show up in the physical body. These stimulations of emotion in the astral body show up as astral colors that creates our aura. This aura surrounds our astral body and can be seen by those who are trained to see it using their third eye.
The manomayakosha (astral body) looks identical to the physical body. However it is more durable than the physical body. It does not feel the effects of heat or cold, nor is it bound by the laws of earth. In the astral body one can fly and penetrate objects.
If the physical body is injured the injury will show in the astral body however it heals very fast compared to its physical counterpart by means of prana. However this body is most adversely effected by emotions.
It is elated by joyful and sublime emotions but it gets injured and feels pain by negative or baser emotions directed towards it. Such injurous emotions can be created by oneself or from other people. This is why in Hindu ethics hurtful thoughts or words are considered acts of violence equal to physical harm.
The vijnanamayakosha (mental body) is the mind of the astral body. However it is of a deeper intelligence that functions beyond the intellectual mind. The vijnanamayakosha (pronounced vig-nyana-maya-kosha) gains it’s strength and abilities through the wisdom we derive from life experiences.
This wisdom comes from lessons we learn from life and also through personal spiritual realizations. The vijnanamayakosha feeds on experiential knowledge. This is different from our normal intellectual function that is mainly gained through memorizing ideas and opinions and basic logic reasoning. Through the vijnanamayakosha we obtain profound insights into life through intuition. The organs of the vijnanamayakosha are the chakras along the spine and in the head.
The astral and mental bodies do not die when the physical body dies. However it is not immortal nor deathless like the soul. These two bodies are discarded when we are reborn on earth. The wisdom, experiences and memory stored in these bodies turn into “seed form” and are stored within the soul. These 'seeds' will reemerge in future lives as our innate personality, abilities or spontaneous spiritual realizations.
At birth, when we get a new physical body we also develop new astral and mental bodies as our personality and experiences develop. We utilize our astral and mental body every time we think, emote or ponder. When dreaming during sleep we are functioning almost entirely in these two bodies. When the physical body dies, the pranic body dies with the physical. After that the astral and mental bodies form our outer bodies, through which we exist in heaven (or hell).