Objective-C synthesize property name overriding

I am trying to understand the purpose of the synthesize directive with property name overriding. Say that I have an interface defined as follow:

@interface Dummy ... {
    UILabel *_dummyLabel;
}

@property (retain, nonatomic) UILabel *dummyLabel;

And in the implementation file, I have:

@synthesize dummyLabel = _dummyLabel;

From what i understand, "dummyLabel" is just an alias of the instance variable "_dummyLabel". Is there any difference between self._dummyLabel and self.dummyLabel?