The whole duck isn't enough

Static is used when a class is created within the same class as the main method. You don't have to use static when creating a new class as long as it's not on the same class as the main method. Could be wrong but that's what I understand.

i don't understand, doesn't all classes have a main method? How can you create a class that is not in the same class as a main method?

That's correct, but as will be mentioned in one of the future lessons: The toString() method is inherited from the Object class. So basically every class has this method by default (like e.g. constructor) and when you call System.out.println(xy) you are acutually calling toString() method. I've acutally found one of the clarification also in lvl 3 (Screen output once again). "The Object class's standard toString() method returns a string consisting of the class name and the object's memory address (in hexadecimal form)." So we basically "override" the default implementation of this method. But as well method overriding (which is not same as overloading) will be taught in future lessons (as your lvl is 18 i think you already know all of those things :)). So for others - it would be more logical if they show you something like this:

public static class Duck {
        @Override
        public String toString() {
            return "Duck";
        }
    }

Then it is quite apparent that we "override" some method which was implicitly implemented somewhere (in Object class). Hope this will help.