What does it mean by "value class" ?

[jezz]

The Assistant said:
"QSqlDatabase is a value class. Changes made to a database connection via one instance of QSqlDatabase will affect other instances of QSqlDatabase that represent the same connection."

What does it mean by "value class"?
I only have one database connection in my application. Should I use a pointer to it everywhere in the program? Or shouldn't I?

class MyApp1:public QApplication {
 
public:
  QSqlDatabase db() {
    return db;
  }
 
private:
  QSqlDatabase db;
}
 
 
class MyApp2:public QApplication {
 
public:
  QSqlDatabase *db() {
    return &db;
  }
 
private:
  QSqlDatabase db;
}

class MyApp1:public QApplication {

public:
  QSqlDatabase db() {
    return db;
  }

private:
  QSqlDatabase db;
}


class MyApp2:public QApplication {

public:
  QSqlDatabase *db() {
    return &db;
  }

private:
  QSqlDatabase db;
}

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Which is better? MyApp1 or MyApp2 ?

Thanks !