Configuration management sync vs active vs staging The documentation on config management talks about a CONFIG_SYNC_DIRECTORY setting, but then there is also mention of CONFIG_ACTIVE_DIRECTORY and CONFIG_STAGING_DIRECTORY setting throughout comments both on d.o and in stack overflow.  

What are these two different setups about?
This has changed, before Drupal beta 14 it was active/staging now it is sync. These are the settings in settings.php:

Drupal 8 beta 14:
$config_directories['active'] = 'sites/default/files/config_HASH/active';
$config_directories['staging'] = 'sites/default/files/config_HASH/staging';

Drupal 8 rc1:
$config_directories['sync'] = 'sites/default/files/config_HASH/sync';