Which type of function is not a member of a class, but can access its private members?

Which type of function is not a member of a class, but can access its private members?

کس قسم کا فنکشن کلاس کا ممبر نہیں ہے، لیکن اس کے پرائیویٹ ممبرز تک رسائی حاصل کر سکتا ہے؟
Explanation

A friend function can access the private and protected data of a class.