5.1.2 Options for getting feedback

Be verbose. xxx is a combination of the following :

The difference between an error/fatal error/hint/warning/note is the severity:

The compiler encountered an error, and can no longer continue compiling. It will stop at once.
The compiler encountered an error, but can continue to compile (at most till the end of the current unit).
if there is a warning, it means there is probably an error, i.e. something may be wrong in your code.
Is issued if the compiler thinks the code could be better, but there is no suspicion of error.
Is some noteworthy information, but again there is no error.

The difference between hints and notes is not really very clear. Both can be ignored without too much risk, but warnings should always be checked.