RMI - IIOP vs Java IDL

Hi,
I have one question again, still confuse me.
As I know Java IDL is the way Java uses
CORBA, like any other languages such as C++, Pascal-Delphi to use CORBA.
RMI-IIOP is RMI under IIOP instead of JRMP,
so our Java based RMI application can
communicate with CORBA application.
So.. both of them have the same functionality,
to communicate with CORBA, when should I use
Java IDL and when to use RMI-IIOP ? in which
scenario ?
Maybe I am not clever enough, I can't really
see the point in Whizlab's explaination and
in this forum explaination about this issue.
Thank you for the help

Alex John

My guess:
1) Java-IDL to allow a Java client to connect to a Corba service
2) RMI-IIOP to allow a Corba client to connect to a Java service.