A story's message, or theme, is what the author wants to teach you through his or her writing. Some stories have a specific kind of message called a moral, or a life lesson. You can find the message of a story by looking at the characters' actions and focusing on what is repeated throughout the story.
The term theme can be defined as the underlying meaning of a story. It is the message the writer is trying to convey through the story. Often the theme of a story is a broad message about life. The theme of a story is important because a story's theme is part of the reason why the author wrote the story.