Foreshadowing is presenting an omen or sign of a future event to let readers know something is going to happen. This literary device allows the writer to reveal just enough information about an event to keep the reader interested in the storyline.
Writers use foreshadowing to alert readers of plot turns and twists before they happen. It allows the writer to tease and entice the reader, reveal small amounts of important information, and build tension within the story arc without giving away too much. Authors use foreshadowing to prevent the reader from being confused when he encounters a plot twist.
Writers must be careful to avoid giving away too many details with foreshadowing. If the writer reveals too much information too soon, the reader may lose interest.