Mac OS 9.x and earlier
In versions of the Mac OS prior to Mac OS X, control panels automatically quit when you closed them. They did not behave the way other applications in Mac OS 9.x and earlier did, which was to remain open until explicitly quit. Sherlock behaved as a control panel in this respect.
Mac OS X 10.0 and later
With Mac OS X, both control panels and Sherlock behave as normal applications.
Each Mac OS X control panel is contained as a "pane" in the System Preferences application. If you open the System Preferences application and close the System Preferences window, System Preferences does not quit. The Dock indicates that the System Preferences application is still open by showing a triangle underneath the application icon.
To get a new window for an application, click its icon in the Dock.
Note: This does not apply to applications such as the Grab utility, which do not show a window when opened.
Quitting an open application
Select the application in the Dock and choose Quit from the application menu. You may alternatively use the Command-Q key combination.
Monitoring system usage
Open applications continue to use memory and system resources until you explicitly quit them. Though an application that is open but not being used generally consumes very few system resources, you should be aware that some applications may be performing significant tasks when not in the foreground. How can you tell the difference? You may use the Process Viewer utility to see the percentage of CPU time and memory being used by an application.
Note: It is normal to see processes in the Process Viewer that do not appear as applications in the Dock. Most of these are components of the operating system.