Allusions An allusion is an a reference to a well known person, event, piece of art, history, myth, or something in popular culture. The reference is a comparison within the writing. It is assumed that the reader has knowledge of what is being referenced. Therefore, an allusion is when a piece of writing tries to hint at a person, place, thing, literature, or art in order to make a clear comparison.
For example: Chocolate is his Kryptonite. To get this reference, the reader would have to be familiar with both Superman and the effects of kryptonite on him!
Some other examples of Allusions can be found here.