What distinguishes a narrative essay from a short story or short memoir

Memoir is a personal story of the past, based on memory. It can be short (like a short story) or it can be book-length. Its focus on memory distinguishes it from the personal essay, which presents a particular insight the author packages in a personal narrative.  the difference between a story and a memoir is Both involve written depictions of personal experiences. ... A key difference is that a narrative focuses on an event, while a memoir centers on an individual, who is usually the writer of the book.

Explanation:

An author may choose to write a memoir in order to describe a personal experience. A memoir allows the author to give readers access to his personal thoughts, feelings, and recollections during an experience, aspects that are unique to the writer and that can be expressed in the writer’s own voice as he reflects on the experience.

the words "strangest" and "unusual" suggest (: