Whether you are standing upright without moving, or when you put your foot ahead of you on the ground whilst walking, gravity settles or compresses you into the ground. As it does so, a balancing act automatically takes place in the body.
In order to achieve perfect balance, whether you are standing either on both feet or on one foot, or even when you are in the process of walking, the body has to align itself vertically with the point of pressure on the feet/foot.