what is the difference between System exceptions and Application

All exception derives from Exception Base class. Exceptions can be generated programmatically
or can be generated by system. Application Exception serves as the base class for all applicationspecific
exception classes. It derives from Exception but does not provide any extended
functionality. You should derive your custom application exceptions from Application Exception.
Application exception is used when we want to define user-defined exception, while system
exception is all that is defined by .NET.