GWT-Ext is a powerful widget library that provides rich widgets like Grid with sort, paging and filtering, Tree’s with Drag & Drop support, highly customizable ComboBoxes, Tab Panels, Menus & Toolbars, Dialogs, Forms and a lot more right out of the box with a powerful and easy to use API. GWT-Ext is basically an interface allowing you to use GWT to create Ext web apps. Very nice.