i also would like to know this. I have music on onedrive, and would like to make it available offline (download it) on the phone.
on the topic, i tried downloading a movie (mkv) and ie11 told me you can find the downloaded file in "downloads" but i couldn't find the file. then in moliplayer, the file was there and I could play it.
Then in data sense, i saw there a section called downloads, and it said it was filled with 250MB (which was the size of the file I had dowloaded). so i could delete it.
So my guess is that this downloads is kinda like a transfer area, and apps can see in it? But we cannot directly access it? Is this new in 8.1 or was it like this in 8.0?
Sorry to hijack but i think it's related.