A fair question at this point might be: what is an App anyway? How do we define one?
I consider the key characteristics of an App to be as follows:
They are self-contained:
They open in a separate window.
They contain only a single display, or contain multiple pages which are linked together by some form of explicit visible navigation.
They do not contain elements, or link through to elements, that are considered to be part of another App.
Any outbound links that lead to other Apps open in new windows.
Any search facilities are specific to that App - only offering results that are relevant to that App and not leading the user away elsewhere.
An app should not be completely reliant on another App in order to work.
They perform a specific function, or offer a specific value.
It should be possible to give an App a reasonably short name and description which clearly expresses what it does.
They are reasonably small.
They offer only a small set of functionality, focusing on providing a solution for a small set of needs, rather than a grand solution for disparate requirements.