Question

As I anderstand:

The abstract factory pattern provides an interface for
creating a family of objects whereas factory method
provides an interface for creating one object.

If this is only difference between these patterns why they are being considered separately?

Answer 1

The factory method is fixed – you can’t change it at runtime.

Abstract factory allows you to create objects with a different factory, which can be selected at runtime, depending on some criteria.

Button button = WinButtonFactory.create(); //will always be a "windows button"
Button button = buttonFactory.create();

on the 2nd like this can be WinButtonFactory extends ButtonFactory or MacOSXButtonFactory extends ButtonFactory. You can pass one or the other depending on the current OS.