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.
Buddhists 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.