Allegory has hidden meanings through symbolic figures, action, imagery, or events, which create the moral, spiritual, or political meaning the author wishes to convey. Allegory is a type of metaphor that can represent real-world issues and occurrences while other metaphors is used to compare two things. Allegories illustrate complex ideas and concepts.
"And now, I said, let me show in a figure how far our nature is enlightened or unenlightened:-Behold! human beings living in an underground den, which has a mouth open towards the light and reaching all along the den; here they have been from their childhood, and have their legs and necks chained so that they cannot move, and can only see before them, being prevented by the chains from turning round their heads. Above and behind them a fire is blazing at a distance, and between the fire and the prisoners there is a raised way; and you will see, if you look, a low wall built along the way, like the screen which marionette players have in front of them, over which they show the puppets."(Plato's Allegory of the Cave)