That's a definition of webpage, but you don't explain why webpages aren't a subset of apps. I saw your comment pre-edit, which said that an app has to be downloaded to a user's device to run, but that also doesn't exclude webpages since an HTML document and its scripts also have to be downloaded to a device to run. Is it something that has to be pre-compiled? Is an html and javascript page embedded in a binary an app? I'm only trying to point out that the word "app" is too ambiguous. We can agree that a book isn't an app, but beyond that the definition is purely subjective.
Sorry for coming off as pretentious, but that's just the default message that comes with create-react-app. And I conveniently disregarded the idea of making a change!