(Critical) is more serious than (Error).
(Error) is more serious than (Warning).
(Remark) denotes additional information to help you understand the context of an analysis.
In dynamic analyses, critical severity is used for Unhandled application exception defects that usually cause the application undergoing analysis to crash. In static analyses, critical severity is used for the most exploitable defects, such as a bounds violation. Addressing these defects is critical for protecting your application against security attacks.
Severity level is a property of a problem type. All problems in a problem set have the same severity level.