What are the characteristics of a parable?

A "parable" is a comparison, similitude, allegory-

-a short, mainly fictitious, narrative from which we learn a moral or spiritual truth.

-a means of explaining a thing by figuratively 'placing it beside' another similar thing.

-a prolonged metaphor in which a series of actions are symbolic of other actions

(Galatians 4:24)(2Peter 2:22).