The word bardo
literally means "an
interval between two things". 'Bar' means 'interval' and 'do' means 'two'.
We can think of this interval in a
spatial or
temporal way. If there are two houses, the
space between them is a bardo. The
period between
sunrise and
sunset, the interval of
daylight, is a bardo. A bardo can be of long or short duration, of wide or narrow expanse.
The bardos as encountered in the Tibetan Book of the Dead describe the passings between various stages of consciousness, e.g. falling asleep and waking up, going in and out of a trance during meditation, and of course dying - the passing from life to death.