Private protected private and not write differences

Public declarations are common member variables and function members and can be used outside of classes throughout the class.
Private member variables and function members are declared privately and can only be used within the declared class.
Protected are declared as protected member variables and function members and are not available outside the class. Can be used within a class.
Use of the keyword is not used by default in the class.

Also note the difference in inheritance when they are.
Public declared in subclass changed to public
The subclass of the protected declaration becomes private
Private declaration is not available in subclasses