Term public private and protected in oop
Object oriented programming terms: public scope to make that variable/function available from anywhere, other classes and instances of the object. private scope when you want your variable/function to be visible in its own class only. protected scope when you want to make your variable/function visible in all classes that extend current class including the parent class. More: (For comprehensive information) https://php.net/manual/en/language.oop5.visibility.php