This documentation describes RichEdit and ITextDocument, which are part of MFC. RichEdit uses TOM, or text object model. The documentation makes repeated reference to "stories":
The GetStoryCount property-get method retrieves the count of stories in this document.
The GetStoryRanges property-get method retrieves the story collection object used to enumerate the stories in a document.
At other places in the documentation, it's a unit of measurement of the document, in a progression like:
character > word > sentence > paragraph > story > page
But what exactly is a story?