Const after operator function c++

I’m learning C++ i saw a const after an operator function.
It doesn’t make sense because the function returns the same value regardless of the const.
What’s the purpose of using it?

using namespace std;

class Person {
public:
    int age;
    Person(int age) : age(age) {}

    int operator *(int &b) const {
        return b;
    }
};

int main() {
    Person *p = new Person(11);

    int a = 19;

    cout << *p * a; // prints 19

    delete p;
}

>Solution :

A const operator behind a member function applies to the this pointer, i.e. it guarantees that the object you call this function on may not be changed by it. It’s called a const-qualified member function

If you tried, in this example, to change the persons age in the openrator*(), you would get a compile error.