What is the difference between function polymorphism and overloading?

What is the difference between function polymorphism and overloading?

Short answer: 
They are the same. 

Long Answer, (and yet less revealing): 

Polymorphism is simply the ability to have many different methods (Or functions, for those who are used to C-Type programs) to have the same name, but act differently depending on the type of parameters that were passed to the function. 

So for example, we may have a method called punch, which accepts no parameters at all, and returns an integer: 

public int punch() 
{ 
return 3; 
} 

We could also have a method named punch that accepts a String and returns a boolean. 

public boolean punch(String poorGuyGettingPunched) 
{ 
if(poorGuyGettingPunched.equals("joe")) 
{ 
System.out.println("sorry Joe"); 
return true; 
} 
else 
return false; 
} 

That is called polymorphism… And strangely enough, it is also called overloading. 

Do not confuse this with overriding, which replaces a function or method with a new one, or rather, hides the old method and replaces it with a new one.