What is 13.1?
A half marathon is a road running event of 13.1 miles (21.0975km, 193 yd). It is half the distance of a marathon and usually run on roads. It is a popular race for relative amateurs, long enough to be a serious challenge but not requiring the level of training of a full marathon.
i wanted to do a long run, but not as long as a marathon, so i ran a 13.1 and came in 2nd place.