One of the cool things about the software we use to track visitor statistics for the Literary Lab is the ability to see what search terms were used to lead visitors here. A lot of people find us by entering "classic plot structure" into Google or whatever search engine. While Davin has written a post about the classic plot structure that you should by all means go read, it's more a commentary than a definition, so I'd like to take a few minutes and talk about the basics of the classic plot structure, which I'll henceforth refer to as the Three-Act Structure.
In brief, the Three-Act Structure is a framework to arrange story elements into a narrative, with pacing and major plot points as goals, a template into which you can pour your characters and events to give it shape. Narratives are constructed in three consecutive sections, or acts. The author has a distinct job to do in each of the three acts. The basic formula is:
Exposition, set-up, inciting incident. Hero is given a goal.
The middle. The hero tries and fails to achieve goal.
The climax and resolution. Hero makes last attempt to achieve goal and succeeds at last or fails forever.
(These are really sweeping generalizations, I know. But I didn't invent the classic plot structure, I just report on it.)
In Act One, we see the hero (a word I use because it's shorter than "protagonist" and I'm less likely to misspell it) in his daily life, whatever and wherever that is. The hero has some internal need, usually, that can't be met in his daily life. Then, something happens to knock the hero off the rails of his daily life. He's been given a problem or a quest. Act One ends when the hero decides to solve the problem or take up the quest. The author's job in Act One is to establish the crisis in the hero's life that the hero must solve. There are lots of tasks involved in doing this job.
In Act Two, the hero struggles to solve the problem or complete the quest. He appears to be having success, though it doesn't come easy. The antagonist/villain fights against him indirectly. At the end of Act Two, the hero, who has been successful all this time, suffers a major defeat at the hands of the antagonist. Usually this defeat is caused by the hero's internal need which he has yet to deal with. This is the hero's lowest point, morally/physically/spiritually. All seems lost.
Lots of times, Act Two actually consists of the hero solving the problem that came up at the end of Act One, only to discover that it wasn't his real problem at all, and that he's got bigger fish to fry, which frying takes place in Act Three at the climax. The author's job in Act Two is to keep the action and the conflict rising toward the climax, and to show the hero attempting to re-establish equilibrium in his world (that is, achieve his goal). Lots of tasks involved in this job, too.
In Act Three, the hero bucks up and decides that he can go on, usually with greater resolve because yes, he's solved his inner problem that was holding him back. Or, he's realized he has this inner problem and is going to confront that. Either way, off he goes to fight the big fight at the Climax, after which there is a short denoument. The fight, of course, can be internal or metaphorical. Or fought with laser cannons; it's up to you. Your job, as author, is to resolve the crisis one way or another (or show how it cannot be resolved) in a manner that is believable within the rules of the story. The climax must seem both surprising and inevitable (except for those stories where you see it coming the whole time and hope the hero will avoid it). Again, lots of tasks are necessary to do this job.
So you have rising action, rising conflict, the possibility of total defeat and then even more action and conflict and then climax. Sometimes the hero dies or is otherwise defeated at the climax. Anyway, that's your classic Three-Act Structure in a nutshell. It gets more complicated as you layer on subplots and themes and other story elements, but you get the idea.
Another way of thinking about the Three-Act Structure is in terms of Action/Reaction/Results. Or perhaps as Problem/False Solution/True Solution. Or Crisis/Loss of Identity/Rebirth. Or At Home/This Is Not My Beautiful House/This Is My New House. Really, the different stories you can tell in this three-part structure are endless.
Now, is the Three-Act Structure of any use to a writer? I think very loosely in these terms when I do my outlining before I've begun actually writing. I also have begun lately thinking in terms of the Action/Reaction/Results 3-part structure when writing chapters and scenes, which gives a nice feeling of controlled flow to the writing. But I do think it's easy to fall into the trap of writing to a formula, which generally results in stories that are predictable, melodramatic, and otherwise suck.
The idea of the Three-Act Structure grew out of Aristotle's basic structure (which interested parties can read about in his Poetics):
Beginning, Middle, End
But Greek plays had only one act and don't divide nicely into the Three-Act template. Roman plays had five acts (as did the plays of Shakespeare and the Elizabethans), but that was to allow for intermissions and snack breaks. Ancient plays were longer than our two-hour movies so there were practical matters to which playwrights and theaters had to attend.
What I think is as useful for a story template as the Three-Act Structure is to divide the story into two types of action: the action that creates the problem, and the action that resolves the problem. This is how real conflict works in real life. You might try writing down the action that creates the problem and then the action that resolves it, and then break those actions down into scenes and see what you've got.
So while the Three-Act Structure might be a helpful organizing tool, I caution anyone against tying themselves too tightly to it. Stories are about who we are and how we solve problems, and I suggest we think in those terms and not so much in terms of "I haven't raised the stakes for my protagonist" or "I need to use my antagonist's minions in this act."
Beginning, middle and end. Start with the end, if you know enough about your story to know who your characters are. Who is he at the end of the story? Then tell us how and why he got there. That is what you are telling us. That is a story.