The hidden cycle: dying, death, rebirth

I am looking for an explanation for my wife about what happens during the dying-death-rebirth cycle according to Buddhist teachings as well as any background readings we can locate. I was explaining the mourning period after the death of a loved one being based on the average time before rebirth (49 days in Vietnamese tradition), and she had made reference to some reading she had been doing that mentioned the phases that must be passed before a rebirth takes place. I also recall a teaching by Thich Nguyen Tang that explained the 6 possible states in which a person can be reborn (heaven, human life, asura, hungry ghost, animal, hell). Is there a unified explanation that exists between the various traditions?