Apocalyptic fiction is
a sub-genre of science fiction that is concerned with the end of
civilization either through nuclear war, plague, comet/rogue planet
strike, or some other general disaster.
Post-apocalyptic fiction is a similar sub-genre set in a world or civilization after such a disaster.
of a fictional work falling within the latter sub-genre can be
immediately after the catastrophe, with the author focusing on the
travails or psychology of survivors, or considerably later, often
including the theme that the existence of pre-catastrophe civilization
has been forgotten (or mythologized) by the remnant society.
Post-apocalyptic stories frequently take place in an agrarian, non-technological future world, or a world where only scattered elements of technology remain.
There is a considerable degree of blurring between this sub-genre of science fiction and that type which deals with false utopias or dystopic societies.