Functionally, gadgets are similar to controls, in that they gather input from or convey information to the user.

But gadgets are implemented differently from controls. Unlike most other interface elements, gadgets are not windows: they do not have window handles, do not receive events and messages, and are not based on TDialog.

Instead, gadgets must be contained in a gadget window that controls the presentation of the gadget, all message processing, and so on. The gadget receives its commands and direction from the gadget window.

To learn more about working with gadgets and the TGadget class, see Class TGadget and Gadget Classes
To learn more about working with gadget windows, see Gadget Windows and Gadget Window Classes