Ever wondered if there was a template you could follow to make sure your plot works?
Well, there is. The hero's journey is a simple plot arc that is used by the vast majority of successful novels and films to a greater or lesser degree. It sets out markers that can be followed to ensure a reader is drawn in, empathizes with the protagonist and is satisfied by the ending.
The basic hero's journey steps are as follows:
1. Introduction to the hero's world
2. Call to action
3. Crossing the Threshold
4. Meet the Mentor
5. First challenge
7. Dark inner moment
8. Final battle
9. The return home
This is not set in stone, there is scope for variation (look up 'the monomyth' and 'the character driven hero's journey') and of course each of these steps can be interpreted in different ways.
And don't think because it's called the 'hero's journey' that it only applies to fantasy type stories. It's not about having a long-haired youth wielding a ruby hilted sword - Crossing the Threshold could be flying to start a new English Teaching job in Greece, the First Challenge could be an ambitious actress's audition upon arriving in Hollywood or the Final Battle might be confronting an offensive boss at the office Christmas party.