A piece of a work which is set before the "present."
A piece of a work which is set before the "present." Even if the work is written in past tense, there is a "present" during which the action is taking place. When the scene shifts so that all the action is occurring at a time earlier than the present of the work, this is flashing back to the past. (It's "flashing" because it's usually brief, but the flashback could be a significant percentage of the work.)