When you toggle it On - PageSnip will rewrite some of the HTML displayed in your browser to add a heavy dashed line around Tables and DIV statements.
This causes the page to "explode" so that you can see how the web page is put together.
You can use the portions of the web page revealed by the Edge Finder to make selections to gather and you can also use it to remove or hide selections.
To toggle the Edge Finder, just right-click and select it from the menu:
Read more about the Edge Finder here.