All life is in a cycle of death and rebirth called samsara. This cycle is something to escape from. When someone dies their energy passes into another form.
Buddhist believe in karma or 'intentional action'.
Through good actions, such as ethical conduct, and by developing concentration and wisdom, Buddhists hope to either gain enlightenment or to ensure a better future for themselves. These good actions are set out in the Eightfold Path, which includes right speech, right livelihood, and right concentration. Good actions will result in a better rebirth, while bad actions will have the opposite effect.
Depending on the actions performed in previous lives, rebirth could be as a human or animal or even ghosts, demi-gods, or gods. Being born as a human is seen by Buddhists as a rare opportunity to work towards escaping this cycle of samsara. The escape from samsara is called Nirvana or enlightenment.
Once Nirvana is achieved, and the enlightened individual physically dies, Buddhists believe that they will no longer be reborn.
Some Buddhists believe that enlightened individuals can choose to be reborn in order to help others become enlightened. Others believe that, when Nirvana is achieved, the cycle of samsara, all suffering and further existence for that individual itself ends.
Anicca - Buddhists believe that nothing is permanent. Everything changes. So this means that things like everlasting souls or eternal gods cannot exist. Buddhism, unlike other religions, does not believe in a creator God or an eternal or everlasting soul.
Anatta - Buddhists believe that there is no permanent self or soul. Because there is no unchanging permanent essence or soul, Buddhists sometimes talk about energy being reborn, rather than souls.
Buddhists believe in life after death because the Buddha taught that human beings are each born an infinite number of times, unless they achieve Nirvana. In the Dhammapada the Buddha states:
Long is the cycle of birth and death to the fool who does not know the true path.Dhammapada
The Dhammapada contains many other teachings about samsara, enlightenment, and Nirvana:
One road leads to wealth; another road leads to nirvana. Let the mendicant, the disciple of Buddha, learn this and not strive for honour but seek wisdomDhammapada
The Buddha taught his disciples not to fear death. This has been interpreted by Buddhists as suggesting that if they live well, their rebirth will be good.
After his enlightenment, the Buddha could remember his previous lives. Some of these previous lives are recorded in the Buddhist scripture, the Jakata.
In Tibetan Buddhism there are many writings about life after death including the 'Tibetan Book of the Dead'. This is a guide telling the dying person how to react and try to ensure a positive outcome of the experiences. It includes descriptions of the bardo states. These are states between dying and being reborn.
Mahayana Buddhism also uses images to teach about life after death. The Wheel of Existence shows the different realms Buddhists believe you can be reborn into.
Belief in life after death may be influenced by the meaning and purpose it gives to the lives of Buddhists.