The term "Hero's Journey" was popularized in Joseph Campbell's book, "A Hero with a Thousand Faces."
The hero's journey is a common narrative archetype
that involves a hero who goes on an adventure, learns a lesson,
wins a victory with that newfound knowledge, and then returns home transformed.
The Hero's Journey is closely tied to the concept of Monomyth, which claims that there
is an underlying pattern to all human storytelling.
This story structure is, of course, more of a suggestion than a rule and many writers use
alternative modes of storytelling.
The beginning of the story needs to ground your narrative in a baseline setting, which the protagonist needs to leave in order to go on a new, life-changing adventure.
Here, both the audeince and the protagonist will learn of a coming change. Sometimes the protagonist will be whisked away with little choice and sometimes protagonist Refuses the Call.
The protagonist gets a ahold of themselves and the story gets rolling.
The protagonist will Cross the Threshold into a new, Other or Special World, and will become committed to the journey ahead.
The protagonist gains new allies, new enemies, and new skills.
Failure, basically. The protagonist isn't ready for the final showdown. The failure is supposed to help the protagonist grown and overcome said failure.
The protagonist(s) prepare for the final showdown.
This section contains the climax of the story. Therefore, everything in your story needs to come together here.
This is the moment of resolution and catharsis for the audience.