The app you're referring to is likely a mobile application that features a short horror story. A short horror story is a piece of fiction that is typically designed to elicit feelings of fear, unease, and dread in the reader. These stories often rely on supernatural or paranormal elements to create a sense of terror, and can range from subtle and psychological to graphic and gory. Overall, the app is designed to provide users with a brief but immersive experience that taps into our primal fears and keeps us on edge. It's a popular genre of fiction and entertainment that has been enjoyed by people of all ages for centuries.