Plot is generally defined as "the literary arrangements of a sequence of events." In other words, a story may be told chronologically (in a straightforward manner where the sequence of time is linear), or the author may choose to "rearrange" those very same elements or pieces of the story to create suspense or drama. In his story "A Rose for Emily," William Faulkner moves backwards and forwards in time, focusing on how the main character (Emily) and the town she's lived in all her life have changed, especially since the story takes place pre- and post- Civil War. Plot is relatively simple to understand. Primarily, it's the Who (the characters), the What (event or happening), the When (time period) and the Where (setting or locale). As Margaret Atwood, a famous Canadian author, will show you in "Happy Endings," plot is perhaps the easiest part of writing fiction.
In his famous work of literary criticism, The Poetics, Aristotle argued that great and lasting works of literature (primarily drama/plays) conformed to what he termed the "unities," the unity of time (usually the work would take place over the course of a day or a week, unity of place (all action generally occurred in the same location, with news of other "outside" events, etc., coming from a character's recent arrival), and unity of action (all action leads directly to the climax of the story).
Similarly, Edgar Allan Poe modeled his Philosophy of Composition, a volume of literary (primarily poetic) criticism, after Artistotle's theories of the unities. For Poe, however, the unities transformed into unity of tone (the narrator sets/maintains a tone present throughout the work), unity of setting (like Aristotle's unity of place, but more broadly and generally rather than specific, including the appropriateness of subject matter), and unity of effect (all action leads to the overall effect upon the reader).
And yet, another literary critic, a German named Gustav Freytag, developed his famous "pyramid" for expanding on Aristotle's and Poe's ideas concerning of the unities. For Freytag, every literary work (including prose now) should include the following parts: exposition, rising action, climax, falling action, resolution. In short, the exposition is the beginning of the work, "the lifting of the curtain," setting the stage so to speak, where we are introduced to characters (usually the primary characters), the setting, and the beginnings of the plot. During the rising action, we learn of motives and desires, "see" actions taken by characters, meet other (secondary) characters, and begin to sense the tension or conflict between them and the actions they've undertaken. The climax generally occurs at the point of the greatest tension or conflict, a central event occurs, an event the reader may or may not see coming. Next, the falling action, describes the aftermath of the climax, what has transpired, reflection upon what has taken place, etc. The last part, the resolution, arrives to wrap up the loose ends, resolve any remaining plot issues, and conclude the story. I've included a humorous example of Freytag's Triangle using the story, "The Three Little Pigs."
The last section, Allegory, deals with stories which involve a set of symbolic parallels. In "Young Goodman Brown," (Goodman is a religious term used in early America, meaning "a good man" but also indicated higher ranking in the church. The same applied to women, Goodwoman, but it is usually shortened to "Goody."), we meet a man recently married to his young bride, Faith. For Hawthorne, much interplay of vocabulary/irony is essential to creating avenues of interpretation and meaning. Young Goodman Brown has to leave town, travelling by foot, and, at midnight (hes, timing is everything), in the middle of the forest/woods, he meets a thinly disguised Devil who tempts Brown to his core. The parallels here are that Brown and his wife parallel the story of Adam and Eve, and although it's Brown who is tempted by the Devil, he remains resolute in his religion, but is convinced his wife (FAITH!) has fallen to temptation. The "was it real?" or "was it a dream?" serve to leave the reader with the same dilemma as Brown.
In the other story, "An Occurrence at Owl Creek Bridge," Ambrose Bierce does two things simultaneously: he combines a story of the Civil War as another Biblical allegory of both the figurative and literal "Fall of Man" (Adam and Eve), but also introduces into literature a new literary technique which came to be known as "stream of consciousness." I don't want to give too much away, but he manages to place the reader directly into the "stream" of the main character's thought process, enabling us to both psychologoically understand and process simultaneously with the character. It is an extraordinary tale, and a popular TV show, The Twilight Zone, even gave a French production of the tale its own episode, something they'd never done before. Please READ the story before you watch the film (it's about 30 mins.).