A tab panel is used to organize widgets on the screen. This related widgets to be grouped and displayed/hidden when a tab is selected. Tab panels help to simplify overly cluttered pages by dividing the content into easily understandable chunks, improving the overall user experience for your users. Though widgets are hidden when their tab is not selected, all widgets from all tabs are still sent to your back end program as one screen, preventing any extra programming on the back-end when tabs are added.
Hint: a newer Tab Panel Layout exists that overcomes some limitations of the regular Tab Panel.