A line segment is a part of a line with 2 end points. A line segment, or as I would like to call it, Line Segment AB, can be used to give you an idea of how much your business has improved or declined. Point A can be considered the starting point (where you began with your business) and Point B can be considered as achieving a goal. You might be close to that goal, or you might be far away from it. Line Segment AB will give you an idea of how close you are to achieving that goal.