Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires immediate attention.

Logs that are used for interactive investigation during development. These logs should primarily contain information useful for debugging and have no long-term value.

Logs that highlight when the current flow of execution is stopped due to a failure. These should indicate a failure in the current activity, not an application-wide failure.

Logs that track the general flow of the application. These logs should have long-term value.

Not used for writing log messages. Specifies that a logging category should not write any messages.

Logs that contain the most detailed messages. These messages may contain sensitive application data. These messages are disabled by default and should never be enabled in a production environment.

Logs that highlight an abnormal or unexpected event in the application flow, but do not otherwise cause the application execution to stop.