An alternate existence after the end of this existence. The concept originated due to a lack of understanding of what it is like to not exist that eventually lead to a fear in non existence and thus allowed the concept of the afterlife to flourish. In today's world some use Quantum Mechanics/Quantum Entanglement or the lack of understanding of qualia to support an afterlife on a scientific level. However overall the belief in an afterlife is on a decline according to recent surveys on the Gallop Poll.
What do we experience in the afterlife?
Passive Theist: Our Soul either goes to Heaven or Hell or is Reincarnated
Christian Theist: I am going to heaven, you are going to hell.
Passive Atheist: The same thing that happens before we were born