function returning this pointer in c++

Question

1st code:

#include <iostream>
using namespace std;
class demo
{
  int a;
public:
  demo():a(9){}
  demo& fun()//return type isdemo&
  {
    return *this;
  }
};

int main()
{
  demo obj;
  obj.fun();
  return 0;
}

2nd code:

#include <iostream>
using namespace std;
class demo
{
  int a;
public:
  demo():a(9){}
  demo fun()//return type is demo
  {
    return *this;
  }
};

int main()
{
  demo obj;
  obj.fun();
  return 0;
}

what is the difference between these two codes as both are working in gcc?i am new here so forgive me if my way of asking is wrong.

Answer 1

demo & fun() returns a reference to the current object. demo fun() returns a new object, made by copying the current object.