The second level is “protected.” Protected properties and methods can be accessed from inside the class they are declared, or in any class that extends them. They can’t be accessed from outside the class or subclass.
While protected properties and methods are accessible anywhere in the object, the third level “private” is more restrictive.
A private property or method can’t be accessed by a subclass of the class it is defined in. If you have a class with a protected property and a private property and then extend that class in the subclass, you can access the protected property, but not the private property.
Hope you may understand~