Summarizing
In the beginning students are taught to retell a story - give a detailed "play by play" of all the events in a story, but as they get older they are expected to give a brief overview of the story, better known as a summary.
Summarizing a narrative text helps students comprehend the plot of the story. Good readers are always taking information from the text and condensing it into a summary-type form. As readers pull out the most important information, they are constantly interpreting what the author is telling them and further developing the summary of the story.
The Somebody-Wanted-But-So-Then formate is a great way for students to give a summary and not a retell.