What does class variable assignment mean ?

int x = 4;
int y = 7:

y = x;    // now    y   contains  4

This isn't true for class variable assignments.  In class variable assignments, members of one class aren't assigned to members of another class.  Then, what does it mean to assign one class variable to another ?

#include <iostream>
#include <string>


class GradeBook
{
public:
   GradeBook( std::string );
   GradeBook() {};
   void setCourseName( std::string );
   std::string getCourseName();
   void displayMessage();
   std::string courseName;
   
};

#include <iostream>
#include <string>


class GradeBook
{
public:
   GradeBook( std::string ); 
   GradeBook() {}; 
   void setCourseName( std::string ); 
   std::string getCourseName(); 
   void displayMessage();
   std::string courseName; 
    
};


int main()
{

  GradeBook gradebook1, another;
  
  gradebook1.courseName = "CS101";
  another.courseName = "CS200";
  
  another = gradebook1;

  
  std::cout << "\n" << "Course Name is: " << another.courseName << "\n";
  
  return 0;
}

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Program output is:    Course Name:  CS101

What does the following assignment statement mean ?
another = gradebook1;