This is where you can add, arrange, and remove content for locations on your site.
The image below shows two widgets used in the sidebar and the results.
To add a widget drag and drop the widget into the desired area.
Note: Make sure to select the desired area before adding widget.
To remove a widget select the widget and drag it out of the area.
Note: Removing the widget will remove all settings and data of that widget. There is a way to move the widget and save the settings.
Note: Select Update when finished editing.
For more information about WordPress Widgets click here https://codex.wordpress.org/WordPress_Widgets.