The Gustav Freytag pyramid is named after a German dramatist and novelist Gustav Freytag of 1816-1895. This story plot pyramid illustrates a general outline of a story with building drama that rises to a climax, and falls to a resolution. Its also broken into five acts;
Exposition provides a setting and introduces the protagonist or focus of the story.
Rising Action comprises of complications of the conflict, troubles are compounded, and drama rises.
Climax to a story is the turning point or major change for the protagonist.
Falling Action has the conflict unravel, and leads the reader to the conclusion.
Denouement (derived from the French word denoer to ‘untie’) includes the resolution to the conflict, a sense of catharsis, and tying up loose ends.
A better explanation of the above can be found here, at Learn the Elements of Style web site