Please see https://forums.bitfire.at/topic/1674/what-is-the-2-letters-after-the-account-name-for-address-books and the links there (especially the manual)
Google caldav and carddav are not supported in DAVdroid as I understand. But I really need it.
Maybe someone tried to implement google support in DAVdroid?
And maybe someone know any alternatives of DAVdroid that supports google caldav and carddav api?
I would appreciate any help and information.