difference between private and public c++ code example

Example: public in c++

#include <iostream>
// Visibility is how visible certain members or methods of class are , who can see them ,who can call them and who can use them
//Visibility has no effect on performance of your program it is ust for organizing code
//Three basic visibility modifers are:
//1 private
//2 public
//3 protected
//default visibility of a struct is public
//default visibility of class is private 
class Entity
{
protected://means all sub classes and base class can access these functions and variables butcan't be accessed outside classes
	int P;
	void InitP () {
		P = 0;
		//initializes P to 0
	}
public://Pubic methods and variables can be accessed inside and outside of the class
	int a, b;
	void Init() {
		a = 0;
		b = 0;
	}
private://only entity class can read and write the variables exeption is friend
	int X , Y;
	void print(){
		// Content
		// only this function can be acessed inside the class unless you use friend keyword
	}
public:
	Entity() {
		X = 0;// can initialize x inside the class but can't access it from outside the class unsless you use friend keyword 
	}

};
class Player : public Entity// class palyer is a sub class of  class Entity
{
public:
	Player() {
		//X = 2;	// Error can't access the private members from base class
		//print();	// can't access it in sub class because it is private 
		a = 1;	// can acces it because it is public in base class
		b = 1;	// can acces it because it is public in base class
		Init(); // can acces it because it is public in base class
		P = 0;	// can access it in subclass because its visibility is protected
		InitP(); //can access it in subclass because its visibility is protected
	}
	 
};
int main()
{
	Entity e1;
	Player a;
	//e1.x;	//error can't access private members from here
	//e1.print(); // error inaccessible due to its visibility being private
	e1.a = 5;//can access from here because it's visibility is public 
	e1.Init();//can access from here because it's visibility is public
	a.a = 5;//can access from here because it's visibility in base class is public 
	a.Init();//can access from here because it's visibility in base class is public
	//e1.P;	//can't access it because  visibility is protected
	//e1.InitP; //can't access it because  visibility is protected
	// a.P;		//can't access it because  visibility is protected in base class
	// a.InitP; //can't access it because  visibility is protected in base class
	std::cin.get();