Order ( high priority to low):
- FATAL ERROR WARN INFO DEBUG TRACE
debugto write debugging messages which should not be printed when the application is in production.
infofor messages similar to the "verbose" mode of many applications.
warnfor warning messages which are logged to some log but the application is able to carry on without a problem.
errorfor application error messages which are also logged to some log but, still, the application can hobble along. Such as when some administrator-supplied configuration parameter is incorrect and you fall back to using some hard-coded default value.
fatalfor critical messages, after logging of which the application quits abnormally.