The afterlife (also known as life after death) is the notion of something, typically spiritual and experiential, that happens to human beings when they die.
There is no widely agreed-upon scientific evidence for life after death or cesation of existence, though some would point to studies of near-death experiences as evidence for the former. In any case, some -- particularly atheists and agnostics of a secular humanist mindset -- hold that we entirely cease to exist. For those who do believe in an afterlife, there are various notions about it. One notion which is common to Judaism, Christianity, and Islam is that human souls go on for eternity to a place of happiness or torment, such as heaven, hell, or purgatory or limbo.
Another concept which is found among Hindus and Buddhists, believe we reincarnate, whether as humans or as animals. One consequence of the Hindu and Buddhist beliefs is that our current lives are also an afterlife, and both Hindus and Buddhists interpret events in our current life as being consequences of actions taken in previous lives. Although there is some scientific research that seems to suggest that humans may reincarnate as humans (see, for example, the writings of Dr. Ian Stevenson and Carol Bowman), there is very little (if any) evidence to suggest that humans reincarnate as animals, or vise-versa.
Some Neopagans believe in personal reincarnation, whereas some believe that the energy of one's soul reintegrates with a continuum of such energy which is recycled into other living things as they are born.
The study of views of the afterlife is a part of Eschatology, which deals with the soul, the resurrection of the dead, the messianic era, and the end of the world.
Many religions hold that after death people get reward or punishment based on their deeds or faith. The Christian Bible, for example, contains the words of Jesus: "The measure you give will be the measure you get." (from the Sermon on the Mount?). For many, believe in an afterlife is a consolation in connection with death of a beloved one or the prospect of one's own death. On the other hand, fear of hell etc. may make death worse.
In view of the eternity of afterlife, some consider regular life as relatively unimportant, except for determining whether or not afterlife follows, and/or what kind. It is just a provisional situation, and the metaphor of a tent as provisional housing facility is used:
Quote from the bible, Corinthians-2, 5:1: For we know that if our earthly house of this tabernacle were dissolved, we have a building of God, a house not made with hands, eternal in the heavens.
Others, including some Universalists, believe in universalism which holds that all will eventually be rewarded regardless of what they have done or believed.
The question whether or not there is life after death is closely related to the mind-body problem, and like that problem is one of the classic problems of so-called rational psychology and hence of one (now largely outdated) notion of the scope of metaphysics.
The belief in the existence of ghosts and other undead is a reflection of the belief in an afterlife.