sourced from: http://thescriptlab.com/screenwriting-101/screenplay/five-plot-point-breakdowns
This video helped me to understand the theory of the 5 plot point which films can be divided into. It takes a few films as examples and completes textual analysis on them to explain the theory. These are moments that change the thrust of the story, and change the protagonist's path or objective.
Lock In: Protagonist can no longer back out or return to the status quo. The previously opened door slams closed behind the character. It propels them forward into the second act.
Midpoint: halfway through the screenplay, either a major success or failure that swings the story in the protagonist's favour or against them. Mirrors the happy or tragic ending.
Main Culmination: AKA the climax. Pinnacle of the protagonists journey. Brings the second act objective to a close. The highest or lowest point.
Third Act Twist: halfway between the main culmination and the end of the story. Monkey wrench thrown into the protagonist's path, which changes their trajectory.