Implementation of overloading, where?

Ok I have my code for implementing overloading in this program. Which part is exactly the implementation of overloading in this source? I am still very confused on overloading of the output operator.

Here is my code for persontype.h:

#include <string>

class person
{
public:
      std::string getNameLast();
      std::string getNameFirst();
      void setNameLast(std::string nameLast);
      void setNameFirst(std::string nameFirst);
      void introduceFirst();
      void introduceLast();
      friend std::ostream &operator<<(std::ostream &os, const person &p);
private:
      std::string itsNameLast;
      std::string itsNameFirst;
};

Here is my code for persontype.cpp:

#include <iostream>
#include <string>
#include "persontype.h"

using namespace std;

string person::getNameLast()
{
      return itsNameLast;
}

void person::setNameLast(string nameLast)
{
      itsNameLast = nameLast;
}

void person::introduceLast()
{
      cout << itsNameLast;
}

string person::getNameFirst()
{
      return itsNameFirst;
}

void person::setNameFirst(string nameFirst)
{
      itsNameFirst = nameFirst;
}

void person::introduceFirst()
{
      cout << itsNameFirst;
}

std::ostream &operator<<(std::ostream &os, const person &p)
{
    os << p.itsNameFirst << " " << p.itsNameLast;
      return os;
}

Here is my main.cpp code:

#include <iostream>
#include <string>
#include "persontype.h"

using namespace std;

int main()
{

      person PersonFull;
      PersonFull.setNameLast("Ann");
      PersonFull.setNameFirst("Heidi");

      cout << "The persons first and last name is: ";
      cout << PersonFull << endl;

      return 0;
}