Fable

A fable is a work intended to illustrate a particular moral lesson. It frequently includes anthropomorphized animals, plants, or inanimate objects, e.g., trees, the North Wind, rabbits, etc. For example, Aesop's fables.

The fable is a type of folk literature, related to the parable which is a similarly short work intended to impart a moral lesson, but involves only human actors (and thus, is more likely to be non-SF). Fables are inherently SFnal.

Allegory is another related genre that strongly relies on symbolism. For instance, "Pilgrim's Progress" by John Bunyan (1678) is an allegorical Christian novel that tells the story of Christian, an "everyman" who goes from the "City of Destruction" to the "Celestial City", carrying a burden. Similarly, Christine de Pisan's Book of the City of Ladies is an allegory for the wisdom and grace that women have brought and can bring to the world. George Orwell's Animal Farm is an allegory of Stalinism and the Bolshevik crushing of the Russian Revolution.

"Fabulist" and "fabulism" is often used a bit more broadly than simply relating to fables. Fabulism includes fables, but also includes other works that includes anthropomorphized animals, inanimate objects, etc., without necessarily including the pithy moral lesson. For example, Richard Adams' Watership Down, Beatrix Potter's Peter Cottontail stories, and E.B. White's Charlotte's Web may be classed as "fabulist", whether or not they convey some pithy moral lesson.