G/A
Because of the call made by one of the Cockpit crew members as they see the Aircraft not in a position to make a safe landing. As simple as that sounds as difficult that is as a lot of people think it is a shame to do so. It is better then burst a few tires or even worse overrun and park in the opposite approach lights or in the localizer antenna.... Aircrafts are designed to fly... they are safer in the sky then in the middle between ground and air. I hope that is short enough to give you a simple explanation when you fell not comfortable then better throw it away and do another one, or, if it doesnt work>> divert!.
NG