The Subselection Tool doesn't have any extraneous options, but it's still one of the most useful tools for drawing and editing your shapes. When you select a shape, line, or fill with the Subselection Tool, it allows you to see and edit the paths that make them up, including the individual vector points and their "handles". You can select one or more vector points and drag them about, or you can select a single vector point and by dragging the "handles" about, adjust the curves to either side of the point to change your shape.