spring aop mix-in class

I was reading folowing lines and I did not understand clearly.
any interface exposed on your mix-in class and delegate any calls to these methods
to this mix-in. Since our class implements Auditable, all invocations for
methods on this interface will be called on our interceptor. Any other methods
are delegated to the target object. If your interceptor class implements an interface
you do not want exposed as a mix-in, simply pass the interface to the
suppressInterface() method of the DelegatingIntroductionInterceptor class.
Now we said that you do not have to implement invoke(), but you can if your
Any ideas, resources,sample code,links, highly appreciated. thanks in advance.