Allegory is a literary technique in which a message or an idea is conveyed through a metaphor. An allegory usually tells a story that is a metaphor for real-world issues or complex ideas. Allegories have been used throughout the history of art because they can make complex concepts comprehensible. These hidden or complex meanings are symbolized by events, actions, figures or images.
George Orwell's work "Animal farm" can be considered an example of Allegory. The work tells the story of animals in a farm that, trying to create a utopic society for themselves, are engaged in corruption and betrail conflicts that symbolize real political conflicts in the Communist Revolution of Russia. Orwell creates characters who are apparently just animals on a farm, to symbolize and represent his critics and points of view regarding the revolution. The animals represent human weaknesses and, their actions, human corruption.
Ambiguity is another literary technique, very different from an allegory. Works written using ambiguity are based on inexactness, they are open to more than one interpretation. Instead of representing a specific story or message, or trying to convey a specific idea, ambiguity creates a puzzle that can never be solved. It generates reflection and it leaves a doubt in the air. The ambiguity is usually expressed through a statement, and sometimes even carried by just a word, instead of being held by an entire story with situations and figures. A statement or word that ties the knot to create a puzzle or vagueness is enough to evoke an ambiguity. Although, it can be a tool to build a character or to base a story on.
An example of ambiguity can be found in the first line of the poem Ode to a Grecian Urn, by John Keats. The poem says “Thou still unravish’d bride of quietness…”. Here, the word "still" can be understood as something that doesn't move, therefore is still, or something that hasn't been changed yet. The ambiguity can't be solved, so it creates a meaning that is open and that can be changed.