The structure of a play means the order that action and scenes are placed for dramatic effect. Think of the Hollywood blockbuster film, Titanic. The film begins with the main character Rose, as an old woman telling her story as the main body of the film is a flashback. From the outset we know she survives the ship’s sinking. When she boards the ship in her story we know what’s going to happen, although she does not.
If the narrative or story was not a flashback and we were unsure whether Rose lived or died, the dramatic experience would be very different. Although there would be increased tension surrounding her fate, we might not empathise or connect with the character as we do by knowing we’re viewing events through her eyes.
Amadeus, the renowned stage play and film, uses flashback extremely effectively and the play begins at the end with one of the main characters, Salieri, as an old man. Too Much Punch for Judy by Mark Wheeler also uses flashbacks to good effect. When structuring work you must consider the emotional or dramatic effect you want to have on your audience.