How is a character arc used in a story?

The Character Arc is the transformation or journey of a character during the course of the story.

Explanation:

The character starts off as one person and gradually change into a different type of person because of the changing developments in the story.

A character arc is the transformation or inner journey of a character over the course of a story. If a story has a character arc, the character begins as one sort of person and gradually transforms into a different sort of person in response to changing developments in the story.