Allegory is a form of extended metaphor,
in
which objects, persons, and actions in a narrative, are equated
with the meanings that lie outside the narrative itself. The underlying
meaning has moral, social, religious, or political significance, and
characters are often personifications
of abstract ideas as charity, greed, or envy.
Thus an allegory is a story with two meanings, a literal meaning and a symbolic
meaning.
Example:
I have found the Ekphrasis
poetry very useful in treaching allegory.
Other examples: Fairie Queen Spenser; Pilgrim's Progress by John Bunyan; Young Goodman Brown by Nathaniel Hawthorne