To allude means to make an indirect reference or mention of something. In literature, authors often use allusions to refer to other works, events, or ideas without explicitly stating them.
The author gives hints or clues about future events in the story. For example, if a character keeps having bad dreams about falling off a cliff, it may foreshadow a dangerous situation later on.
A figure of speech that compares two unrelated things by saying one is the other. Like saying "The world is a stage," comparing life to a theater stage.