widget

A software widget is a relatively simple and easy-to-use software application or component made for one or more different software platforms.
A desk accessory or applet is an example of a simple, stand-alone user interface, in contrast with a more complex application such as a spreadsheet or word processor. These widgets are typical examples of transient and auxiliary applications that don't monopolize the user's attention.
On the other hand, graphical control elements (GUI "widgets") are examples of reusable modular components that are used together to build a more complex application, allowing programmers to build user interfaces by combining simple, smaller components.

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