The module provides utilities for controlling the module status of all modules in the whole installation by a single drush command. The configuration is done by defining "master modules". "Master modules" are (in most cases) custom modules or features, that provide dependencies to all modules that are needed to run the site. In combination with Features and maybe some custom code and scripts the whole site configuration can be managed via that approach.
Master status
drush master-status shows the state of all modules that are "master", required by master modules or are redundant (enabled but not required).
Master execute
drush master-execute ensures all master modules and their requirements by enabling them. It also disables and uninstalls all modules that are not required by the master.