Gadgets are small, standalone program files that are inserted into user interfaces(shells) as control panels, similar to applets or widgets. They are graphical utilities supported by popular operating systems and provided as gadget collections.
It is a relatively small, delimited area, a rectangle or circle, within which a dialog with computers and devices on the networks can be conducted using the computer mouse (and possibly the keyboard). This gadget (according to the dictionary: small device or gizmo) can be found either directly on the screen, but much more often in windows or requests, where some network unit or computer asks questions to the user.
Gadgets can be calendars, map snippets, time overlays, display of charge states, or superimposed phone numbers. In the web world, gadgets are usually called widgets.