How does SharePoint synchronize with Word app?

I have read that when creating a document in Word for the iPad, the document automatically saves to OneDrive and synchronizes automatically.

However I don't want this. I want to work on (edit) a document that is stored on my corporate intranet on SharePoint (hosted privately and NOT Office 365 SharePoint).

So my question is, is the document I am working on automatically synchronized to SharePoint if I have downloaded it from SharePoint?

Follow-up question - is my SharePoint document also stored on OneDrive without my authorization?

Thanks!

- Thom