When I think of an application, I think of something used reasonably directly by an end-user. From the linked article, things like IntelliJ IDEA, the Maestro Ma

When I think of an application, I think of something used reasonably directly by an end-user. From the linked article, things like IntelliJ IDEA, the Maestro Mars Rover controller, Minecraft, Hadoop, etc. Admittedly, this is just my personal definition, "app" is a pretty loose term. For, say, the "Google Sheets web app", I'd say the entire piece of technology, frontend and all backend services, combine together to provide an application. But if the Google Sheets web frontend depends on, say, 20 different backend services, I wouldn't say that any one of those services is an app on its own. Each service makes up a part of the backend of one-to-many apps. And, from what I know of Google's tech stack, different services might be written in different languages - primarily Java, C++, Python or Go.