The Hero's Journey is an archetypal story pattern, common in ancient myths as well as modern dayadventures.
The concept of the Hero's Journey was described by mythologist Joseph Campbell in his book The Hero with a Thousand Faces and refined by Christopher Vogler in his book The Writer's Journey.
It can be boiled down to three stages:
Departure: the Hero leaves the familiar world behind.
Initiation: the Hero learns to navigate the unfamiliar world of adventure.
Return: the Hero returns to the familiar world.
More elaborate taxonomies usually include the following stages, not all of which need be present:
Crossing the First Threshold: The Hero must make a conscious, willing decision to embark on the adventure and leave the known world behind. This isthe First Threshold. The Hero may have to defeat Threshold Guardians, who are not necessarily adversarial but do test the Hero's resolve. Down the Rabbit Hole is a special case for young heroines embarking on supernatural adventures.
The Land of Adventure: the Hero enters a strange, dreamlike realm, where logic is topsy-turvy and the "rules" are markedly different from the ordinary world. Carl Jung identified the Ordinary Realm with the conscious mind, and the Realm of Adventure with the subconscious mind.
The Belly of the Whale represents a symbolic death for the Hero: the Hero is defeated and killed, his flesh scattered, ready to be reborn and emerge as a new person. If you think the symbolic death ought to come later, don't worry: The Writer's Journey omits this step altogether in favor of a Resurrection step just before the end.
Road of Trials: the path out of the Belly of the Whale. Usually the meat of the story; The Writer's Journey calls it Tests, Allies, Enemies, while Booker goes into detail on different types of tests (deadly terrain, monsters, temptations, deadly opposites, and a journey to the underworld). Stops along the way might include:
The Shapeshifter: someone you don't trust but nonetheless need for his or her help/information
Night Sea Voyage: the Hero must sneak into the Big Bad's Elaborate Underground Base and retrieve something or someone. Campbell noted that theseStealth Runs were usually at night and often involved water; hence the name.
Link's initial attempt at rescuing Aryll from the Forsaken Fortress in The Legend of Zelda: The Wind Waker is a near-perfect example of one of these.
Perhaps the best known example is the infiltration of the Death Star by Luke Skywalker to rescue Princess Leia.
Time out just before the big battle: the Heroes gather around a campfire and prepare for the battle, tell stories, confess their feelings, etc. It reminds them of what's at stake, and serves as a breather after all the action of the Road of Trials.
Apotheosis / Fight against the Big Bad / Ultimate Boon (These are typically very closely related, often intertwined.)
Apotheosis: The Hero comes to view the world in a new and radically different way, either because of a critical breakthrough he's made or some crucial information he's uncovered. If it is something to do with himself then this is a good time for an I Am Who?.
Ultimate Boon: getting the reward the hero's been chasing all this time, often but not always a MacGuffin.
Refusal of the Return: At this point in the story, the Hero has mastered the strange world he was thrust into. He probably has earned a permanent place here, if he wants it. He may even want to stay, but usually there are forces at work that propel him home.
The pattern of the Hero's Journey can be found in shows ranging from Star Trek to Buffy the Vampire Slayer. George Lucas claims to have used it as a guide when writing Star Wars. Traditionally, the Hero's Journey was cyclic; a female Hero's Journey is more likely to be cyclic than a male's. Buffy The Vampire Slayerfits this to a tee; the movie is the first cycle, and each season roughly corresponds to one additional cycle. The Journey game intentionally fits this model exactly, even referring specific steps in the soundtrack's titles.
The Harry Potter books can also be seen to be cyclic in this fashion, although the journey was followed more closely in the earlier installments. The sixth and seventh books are arguably one cycle divided into two parts. With the final book having been split into two films, the last three films kind of form their own mini-trilogy, with each installment covering a step in the departure-initiation-return model. An interesting element is the fact that in the first five books/films, the Muggle world is the ordinary world and Hogwarts is the world of adventure, but in the Prince/Hallows duology/trilogy, Hogwarts has become the ordinary world and now it is the world beyond Hogwarts which is the world of adventure.
Compare Campbell's description of the journey with Booker's The Seven Basic Plots, especially the plots of Overcoming the Monster, The Quest, and Voyage and Return. Like Campbell, Booker invests a lot of symbolism in the various elements, to the point where messing up the symbolism kills the story for him (for example, he calls Star Wars flawed because they rescued the princess way before they killed the Big Bad, when ideally those should happen at the same time, since the death of the Monster causes the release of the Anima).