The word polymorphic means many forms (poly = many, mophic = forms).
So, polymorphism happens when an object can take on many forms. It really has to do with the instance that is created.
So, a person is a mammal, and an animal - that's two forms they can take on. A person can also be a spouse - that's another form they can take on. A person can be a dentist or a programmer - those are other forms.
In this scenario, if person were a class, maybe mammal would be a superclass, and perhaps animal would be an ancestor class. Spouse, programmer and dentist all seem like roles to me, so those might be modelled as interfaces.
So, extending a class, or implementing an interface, are ways that an instance of a subclass or implementing class can be polymorphic. That's what polymorphism is all about. Now, how that applies to your question is another story.