Flashback
Flashback is a writing technique where the writer narrates the story's past in the midst of the ongoing presence of the plot. Flashback is a crucial tool for the writer to create suspense and foreshadow what is coming next in the story. It also is a way for the writer to describe the characters by using their past actions.
Example 1: In the movie "Titanic," when the old Rose narrates her story on the ship, a flashback of her old self comes on the screen.
Example 2: In stories when a girl is afraid of swimming in the present, the writer uses flashbacks of how she almost drowned once, and hence the fear was born.