While F4 is the default button, you can customize the hot keys used to activate it, just as you can with other Mission Control and full-screen features. These options can be used to greatly enhance your use of Dashboard.

While the overlay mode is perhaps more convenient, using a separate space may be a quick way for you to hide anything on your screen from onlookers, as a quick press of the F4 button will eliminate everything except for the Dashboard. Once done, you will no longer see an overlay but instead have your view shift to the space containing the widgets. To do this, go to the Mission Control system preferences and check the option to Show Dashboard as a Space. The first option is to have Dashboard appear in its own space (for Lion and Mountain Lion users) where, with the system's full-screen capabilities, you can set it to occupy a separate full-screen environment. However, if you would like, you can make some modifications to this and have widgets appear in their own space - or even have them be embedded on your desktop. This is the setup most users are accustomed to. The default behavior for Dashboard is to activate when a hot key is pressed (the default being the F4 key), where the system will present the dashboard as an overlay to your current desktop. Apple's Dashboard feature in OS X is a convenient way to access widgets for looking up information on your system.

Mac os dashboard widgets