All widgets work the same, generally:
You create or define an instance of a widget.
You can preset attributes of a widget, such as its initial value or a label to be displayed.
Widgets can react to different inputs from a user. The inputs are gathered by a handler or a Python function that is invoked when a user performs some action on a widget; for example, a function could be set up to call the handler if the user clicks on a button.
The value of a widget can be used later in your script in the same way as any other variable; for example, you could use a widget to determine how many circles to draw.