A friend who knows: in most cases, our lives are the most common type of friends. That is, a friend who saw the page saw the eyes when going to school or to work, might not be very much, but they greet every time we meet.
Friends and acquaintances: In most cases, our lives would be very different kind of friends. Ie, a friend who saw the eye when going to school or to work. May not have a lot of camaraderie I salute every time they met.
Friends who know: most of the time in our life will have this type of friend most. That is a friend to see see eye when to go to school or go to work, may not close กันมาก but was greeted every time meet