Firefox for Enterprise splits the profile into a local part and a roaming part on Windows accounts that use roaming profiles Where is the documentation on this?

I'm seeing that that the profile is split into two parts: %localappdata%\Mozilla\Firefox\Profiles\<profile name> and %appdata%\Mozilla\Firefox\Profiles\<profile name> This is a GREAT thing... I believe that the large part of the Mozilla profile (caching) is put into %localappdata% and bookmarks and other settings are in the %appdata% (roaming part). If this is the way it works, that would help to make our roaming profiles much smaller. Is there any documentation on this? I'm particularly interested to find out what happens to a users existing Mozilla profile when we install Firefox for Enterprise. Is a new profile created, or is the existing profile split? TIA