Narrative structure refers to the organized framework that dictates how a story is told, including the sequence of events, the perspective from which the story is presented, and how these elements are interwoven to create meaning. In 'Moby-Dick,' this structure plays a crucial role in shaping the reader's understanding of themes and symbolism, as Melville employs non-linear storytelling, multiple points of view, and rich layers of symbolism to enhance the narrative experience.