The narrative arc is the plot in the story, a series of events arranged in a sequence. These events create conflict for the protagonist. Often a narrative arc has five parts: exposition, rising action, climax, falling action, and resolution.
A character arc tracks how a person, generally the protagonist, changes over time as the story progresses. The protagonist evolves in response to the conflicts presented by the narrative. Secondary characters can also have arcs, but generally they are not as pronounced as the protagonist’s.
Narrative and character arcs have different purposes. In a narrative arc, a character starts at an external point “A” and ends up at point “Z.” In contrast, a character arc is the protagonist’s inner journey. The protagonist is in one emotional place at the beginning of the story and reaches another emotional place by the end.
Writers sometimes find it difficult to keep the two arcs in balance. A common mistake is to have loads of plot but no character growth. Another problem is a lot of character growth in a story where nothing much happens. If the plot doesn’t test the protagonist sufficiently, then readers won’t believe in the protagonist’s internal growth. Great growth requires great struggle.
Think of narrative and character arcs as two parallel journeys. One is external, while one is internal, and both inform the other.