Since this period of time is very important for one’s future rebirth, a book, known as the Tibetan Book of the Dead, gives information about how to identify the different stages after death, and rituals to perform to ensure a good rebirth.
There are actually three bardos or stages after death.
(1) The moment of death
(2) Visions of various Buddha forms
(3) Karmically-dirven visions of men and women in yab-yum form, which causes rebirth