Have you ever run straight toward someone you like, the moment you see them? If your answer is yes, then why didn’t you choose a more winding or zigzag route? Why does a straight line take less time than any other paths?
In the 2-dimensional Euclidean geometry, the straight line from two random points is always the shortest. The straight line in this context means that we draw a line from A to B with A and B are the only points connecting the line. For example, figure 1 and 2 are not a straight line because they have other points between A and B. While figure 3 is a straight line because A and B are the only points between themselves.