2.4.3. About Log Categories

Log categories define a set of log messages to capture and one or more log handlers which will process the messages.
The log messages to capture are defined by their Java package of origin and log level. Messages from classes in that package and of that log level or lower are captured by the log category and sent to the specified log handlers. As an example, the DEBUG log level results in log values of 300, 400 and 500 are captured.
Log categories can optionally use the log handlers of the root logger instead of their own handlers.