A parable is like a metaphor that has been extended to form a brief, coherent fiction. Unlike a simile, its parallel meaning is unspoken, implicit, but not ordinarily secret, though "to speak in parables' has come to suggest obscurity.
Parables often involve a character facing a particular moral dillemma, or making a questionable decision and then suffering the consequences of that choice. Though not every moral narrative is a parable, many fairy tales can be viewed as extended parables. Though parables often have a strong suggestion of how a person should behave or believe, many are simply explorations of a concept from a more neutral point of view. Aside from providing guidance and suggestions for proper action in life, parables give people a metaphorical language which allows them to discuss difficult or complex ideas more easily. Recently there has been some interest in the field of contemporary parable, exploring how modern stories can be used as parables in our current culture.
Parables are strongly favored in the expression of spiritual concepts. The best known specific source of parables is the Bible which contains numerous parables told by Jesus Christ and others. Besides the familiar parables of Jesus in the New Testament, such as the Good Samaritan and the Prodigal Son, there are many beautiful examples of the parable in the Old Testament, that of Nathan, for instance, in 2 Samuel 12:1—9, that of the woman of Tekoah in 2 Samuel 9:1—13.
Parable and allegory are often treated as synonyms, but are well distinguished by H. W. Fowler, in Modern English Usage. "The object in each" said Fowler, 'is to enlighten the hearer by submitting to him a case in which he has apparently no direct concern, and upon which therefore a disinterested judgment may be elicited from him." Then it dawns upon the listener or reader that the conclusion applies equally well to his own concerns.
As Fowler distinguished them, parable is more condensed than allegory: a single principle comes to bear, and a single moral is deduced. Medieval biblical criticism often treated Jesus' parables as detailed allegories, but modern critics universally regard these interpretations as inappropriate and untenable.
Like a fable's narration, a parable should relate one simple, consistent action without extraneous detail nor distracting circumstances. In Plato's Republic, parables like the shadows in the cave embody abstract argument in a concrete, more easily grasped narrative.