You told me what it was, but you didn't tell me how it works...
Let's talk about GMC, Motivation-Reaction Units and Turning Points. GMC is Goal, Motivation and Conflict, otherwise known as "Deb Dixon's book".
1) What do they want? 2) Why do they want it? 3) And why can't they have it?
Dwight Swain did something similar in Techniques of the Selling Writer, but called it motivation-reaction units.
1) What causes something to happen? 2) What happens in reaction to that stimulus?
Mckee, in his ground-breaking structural work, Story, talks about how turning points spin the story and increase momentum.
All valid ways to look at plot. In a plot-driven story, event B is always caused by event A. So GMC is pretty much A>B>C>A>B>C, Motivation-reaction units are A>B>A>B and Turning Points are A>B>C>XX>A>B>C>XX2.
Plots are linear and look a little like algebra.
In other words, if I want John back in school, I need a reason.
In organic structure, we start at point A, but how we get to point D is different. In a linear plot, you'd see John get a pink slip and walk past a Workers Retraining poster. In an organic, character-driven story, you'd see John in a crappy job, staring at the ceiling in bed, a stack of bills on the counter, his kids in a rundown second rate school and his fear that maybe that's all there is, maybe he can't get his kids out of poverty.
By the time John walks into the admission office, you know why he's there, but there's no one specific goal or motivation because his goals are as complex as his motivations.
Linear-John is easy to flesh out because his character only needs to be developed to the point of supporting the plot. I can easily give John gorgeous blond hair, dazzling blue eyes and an Armani suit, because for the purpose of the plot, he's a blank slate.
Organic-John is defined by his circumstances and character. He's got kids, he's got a crappy job--they live in a ghetto. That means he might wear a suit, but if he cares about his kids, it's the Sears clearance suit and his gorgeous blond hair is shaggy and unkempt, or military tight so it can go longer between cuts. Maybe he cuts it himself and messed up one side. Maybe he's too proud to ask for help, so he's always hungry.
The difference is depth.
It's not easy to write an organic story. The underlying structure is logical, but that logic is the result of many plot threads coming together that don't always appear logical on the outside--although they are true to your character's internal logic.
John might not get to school because of a pink slip--but he does get to school. In an impressionist painting kind of way.