Eschatology
Eschatology is the branch of theology concerned with the ultimate destiny of individuals and the cosmos: death, judgment, heaven, hell, resurrection, and the end of the world.
From the Greek eschatos, last, eschatology asks what comes finally. Christian eschatology includes doctrines like the second coming of Christ, the resurrection of the dead, the last judgment, the new heavens and new earth, heaven, hell, and (in some traditions) purgatory. Jewish eschatology centers on the coming of the Messiah and the world to come. Islamic eschatology has the Day of Judgment and a detailed account of paradise and the fire. Hindu and Buddhist traditions handle the same set of questions through cycles of rebirth and ultimate liberation.
Within Christianity, eschatology splits into individual and cosmic branches. Individual eschatology is about what happens to a single soul at death: judgment, heaven or hell, possibly purgatory. Cosmic eschatology is about the end and transformation of the world as a whole — a single culminating event (linear, in mainstream Christianity) rather than an endless cycle. A third axis is realized versus future eschatology: is God's kingdom already present and partially realized in the church, or entirely future, or both?
Eschatology is worth understanding because it drives an enormous amount of religious behavior. Beliefs about the afterlife shape attitudes toward death, grief, risk, political engagement, and environmental stewardship. American evangelical politics has been dramatically influenced by specific eschatological frameworks (dispensational premillennialism in particular), with consequences ranging from foreign policy toward Israel to skepticism about climate action on the reasoning that the world is about to end anyway.
From a secular perspective, eschatological claims are both the most distinctive and the least testable parts of any religion. They offer comfort in the face of death and they also generate predictions that, in every case where they have been specific and near-term, have failed. The sociologist of religion is interested in how traditions maintain credibility through failed predictions; the philosopher of religion is interested in whether the concept of an afterlife is even coherent.