See: List of control panels
A control panel (CDEV) is an item under System 7 (until, but not including, Mac OS X) which lets Macintosh users adjust system preferences and settings.
Unlike the Control Panel desk accessory of System 6 and earlier, control panels under System 7 and all subsequent versions of the Classic Mac OS can be opened in separate windows.
As of Mac OS 7.6, some control panels have actually become mini-applications in their own right. These are the so-called APPC control panels.
Under Mac OS X, System Preferences replaces control panels. Control panels from Mac OS 9.x can, however, still be used (despite a few restrictions).