(1) A Windows Vista desktop panel that holds mini applications (gadgets) such as a calendar, calculator, stock ticker and Vonage phone dialer. It is the Windows counterpart to the Dashboard in the Mac. See Windows Vista and gadget.

(2) A feature in the Firefox Web browser that displays history, bookmarks or any bookmarked page in a scrolling window. IE has similar capabilities in its Favorites Center, but does not refer to the window as a sidebar.

(3) A Windows 3.1 shell that replaced Program and File Manager and streamlined the desktop. Originally developed by Mike McCue of Paper Software, it was later acquired by Quarterdeck.

(4) A generic term for an auxiliary window on screen that is displayed alongside the main window.