I didn’t realize the usefulness of this feature in Mac OS X until recently. As you can see, almost every operating system uses a hierarchical file system, where files are stored in nested directories. In user-speak, this would mean that files are stored in folders and subfolders within the storage media, whether it be an optical disk, a flash memory device, or a hard disk.
This system poses some ‘limits’ in organizing files. When the files become voluminous in number, it may be hard to locate each file within the myriad of folders and subfolders. An indexing utility such as Spotlight (and also Beagle in Linux and Google Desktop in Windows) may be the solution, but the lack of being able to store search results means that the search needs to be repeated over and over again.
In Mac OS X, this problem is partly solved through the use of Smart Folders.These ‘virtual folders’ perform one task — they present a list of files meeting a preset criteria. This means, as a smart folder is opened, a list of the latest search results (whose parameters are set in the folder) is shown. So, if the folder was set to show a list of most recently accessed files, it will show the latest files accessed at the moment it is opened. It may appear that the folder contains actual files, but it actually contains links to the files being shown.
Here are the steps to create a smart folder in Mac OS X:

Easy does it!