Defined methods are methods that you have written, or are using correctly based on the given situation. If a method is referenced, it only means that you (or other methods/objects in your code) are calling them. However, just because a method is referenced doesn't mean that their is anything defined for it, or it could be defined incorrectly. If example you're using open source libraries that may have been installed incorrectly (I have done this way too many times) you'll get a ton of referenced methods with nothing defined for them. Hope that helps!