There are different purposes for writing. Authors' can write to inform or entertain.
When authors write to entertain, they write a story with characters and problems and solutions. These stories are usually fiction.
When authors write to inform, they write summaries about stories they have read or they write "how to" paragraphs. "How to" paragraphs explain by using first, next, then, and finally at the beginning of sentences. These paragraphs are non-fiction.