Perhaps I overlooked it, but I didn't see if you were referencing a specific book, so I'll answer in generally terms. Books like short stories have protagonists and antagonists. The Protagonist is usually the hero, and the antagonist works against the hopes, dreams, beliefs, and etc. of the protagonist.
Characters come in two types dynamic (also known as fat) characters who grow, develop, and change through the story. They help drive the plot of the story. The other type of character is a static (also known as flat) character. They are not well developed, and they serve as a tool for the author to develop plot points or significant aspects of the dynamic characters.