Allows you to specify which post/page ID to display recent comments for (or show them all). Simple options for display format as well.
The ID number can be found by hovering over the post or page title while in the "All Pages" or "All Posts" list view WordPress panels. The number will show itself after "post=" in your browser's add-on bar (usually at the lower left hand corner of the screen).
You don't have to limit the comments to one post or page, though. You can show all your posts/pages by typing in the number 0 (zero) instead of a post number.