In narrative writing, you write simply to tell the story to the reader. You will explain the plot, write about the characters and describe the setting of the story as the plot develops. You'll describe a story but not offer up intricate details that will allow a reader to see every detail of the story in their mind.
Descriptive writing doesn't rely on the plot as much as on details and vivid descriptions to convey the story. Describe each character using imagery and diction that will allow the reader to see, in their mind's eye, the character for himself. Describe the setting in great detail to give the reader a full visual image of what occurs in the story.
Narrative writing doesn't emphasize adjectives to give the physical details of characters, setting or events in the story. Unlike descriptive writing, narrative writing uses the first person to relay the author's opinions, values and memories; it is more general, while the content of a descriptive piece focuses on one event, object or place. Sometimes, the author will use the narrative writing style to speak about the past or the future in general terms. The tone is casual and conversational.
Descriptive writing focuses on conveying the author's feelings and thoughts to the reader through visual images and highly descriptive diction. Narrative writing doesn't focus on the reader's understanding of the author's world as much as descriptive writing does. In descriptive writing, you may write in free-form while in narrative writing, you usually have to follow the five-paragraph model with an introduction, body and conclusion. A descriptive work evokes emotion.