Thank You for comments.
First, Vox was a single-playlist player. It tried hard to stay
away from being a "Library". Users appreciated this, but some of
them were, like, "why only one playlist? I want many playlists,
like in xxxx-player on windows!". So the Playlist was replaced by
Collections.
But then other users stepped in, "why so many Collections when
we loved Vox for simplicity, bring back one-playlist mode!". So we
added back the "Playlist", which is , in turn, a Default
Collection.
So, to answer Your first question, Collections are
playlists.
Because Collections are not part of library, they are not sorted
per artist or album - they are controlled by user only - what You
put there, stays there, be it artist or album or arbitrary list of
tracks. It's ok for users who like to manage everything on a
file-folder level - they want to drop files from Finder onto Vox
and manage their playlists manually.
But then others, who accustomed to iTunes, said, "why there's no
Music Library in VOX? How do I add music to collections? Why isn't
all my music automatically displayed?", and the idea of Loop was
born. Loop is a cloud - based downloadable music library. Currently
it uploads Your music and represents it in sortable form, so in
Loop, You can see music sorted per artist or album.
Regarding sharing Collections between OSX and iOS app - that's
not the case currently, but I think in future it will be possible
to share them through Loop.
