Widgets can be added around your measurement to do things that do not have influence on the procedure of your measurement. For example, a Plot can be used to visualize your data.
Adding and removing a widget
Widgets can be opened or added at any time, also during a running measurement.
Other widgets like Plot or Monitor can be dynammically created using the menu "Window". Just closing these widgets, does not remove them, they are just hidden. To remove them navigate to the widget via the menu and click "Remove ..."