From the website
"Narrative Arc and the prototypical “Plot Diagram” are key learning tools for building literature comprehension and appreciation. Plot diagrams allowsstudents to pick out major themes in the text, track changes to major characters over the course of the narrative, and hone their understanding of literary structure, meeting many Common Core Standards for English Language Arts (CCSS.ELA-Literacy). In addition, these concepts give students a fuller understanding of classroom texts as well as stories present in their favorite books and movies. Below is the basic structure of a plot diagram."