Tibetan word for inbetween state. 

It describes the experiences of a consciousness after death but before it has been connected to a new body. 

Bardo is the state in which a consciousness can either attain enlightenment or be returned to the cycle of rebirth. Bardo lasts for 49 days following death. During this time 100 deities appear to the deceased. If these are all recognized as illusions, then the deceased attains enlightenment. 

• Bardo of Death: dissolving into the white light. This bardo passes very quickly, and most people do not even notice it. Those that do have a chance to enter the door to the spiritual world, bypassing the bardo fo the afterlife.
• 1st Bardo: the soul starts to encounter spiritual beings that may be frightening because of their power. They are accompanied by terrifying lights and sounds.
• 2nd Bardo: Spiritual travel, where the soul travels the ocean of consciousness. The dangers are guilt and fear, for someone who has not done sufficient spiritual training. A soul may be caught here, unaware that it has died and unable to attain enlightenment. The goal of the soul in the second bardo is to wake up and lucid dream, so it can move toward a state of spiritual awareness. A guide, saint, or guru can help guide a soul out of this bardo.
• 3rd Bardo: Reincarnation. A soul is presented with images, and its attraction or repulsion from those images determine where it will be reincarnated. 

Reference: http://www.spiritualtravel.org/OBE/afterdeath.html