I'm not sure I really get what the author is trying to say by app versus business.

In terms of what Evernote (and Dropbox for that matter) did, there is a really simple term for this: execution. It is what separates those companies from their competitors in an industry that most probably saw too competitive. This video about Dropbox shows how they did it and I imagine Evernote's success story is no different:

http://www.socrated.com/user_courses/226?content_item_id=168...