Once you've grown comfortable with the layout of the Search dialog box, you may notice the little Save button in the upper-right corner. That button generates a Smart Folder—a self-updating folder that, in essence, performs a continual, 24-hour search for the criteria you specify. (Smart folders are a lot like smart albums in iPhoto and iTunes, smart folders in Mail, and so on.)
In truth, the smart folder performs a search for the specified criteria at the moment you open it. But because it's so fast, and because it's always up to date, it feels as though it's been quietly searching all along.
Figure 3-13. Mac OS X can preserve your search as a smart folder on the desktop. (If you turn on Add to Sidebar, you'll also make the smart folder available as a single-click icon in your Sidebar.) You can stash a smart folder in your Dock, too, although it doesn't display a pop-up menu of its contents, as normal folders do.