Microsoft's Project Madeira shows how the lines continue to blur between what an app is and what a service is. In this case, the Project Madeira basic business apps for Windows, iOS, and Android exist within Outlook, so users can access them without ever leaving Microsoft’s email program.
If that seems confusing, consider how the Outlook apps for iOS and Android include a calendar, but without breaking the calendar portion out as a separate application. That’s how Madeira works.
Technically, Microsoft defines Project Madeira as a public cloud service (or software as a service) for Windows, iOS or Android devices, running on top of Microsoft Azure. It just happens to run within Outlook. The Madeira services are designed for small businesses with 10 to 100 employees—small enough, according to Microsoft, that they have neither the incentive nor the funds to invest in an enterprise resource planning system.