If you change the settings and don't see any results, click this button. As you can see, pretty much useless on most images. The default setting is 2 pixels. To make it match the image edges exactly, set it to zero. Controls how closely Quark follows the edge of the non-white area.
Smoother is less exact.
Controls what shades are considered non-white. In this example, the path created in Photoshop has a mistake in it. There is a bump in the giraffe's neck that needs to be smoothed out. The steps to edit a path are simple. With the content tool, you can click on the path and adjust the anchor points and adjustment handles to make it conform to the shape you like.