Widgets have become common in GUI frameworks, and nowadays even a user can easily interact with and configure them. For our purpose, we define the widgets as elements of interaction that are reusable. They are those graphical elements, which are important pieces of the human-machine interface.

For a Kivy framework, the widgets play an important role, not just because Kivy is a graphical framework, but also because it intends to organize the GUI as a tree of widgets with a root widget in which the other widgets live. Kivy itself has a bunch of predefined widgets that you can use in your app or as part of your own widget. The special kinds that we will be describing in this chapter are layouts, which help us in a visual organization of our tree of widgets.