Whereas SWT provides access to the widgets as defined by the window system, JFace adds structure and facilities for common UI notions. The UI team describes JFace as follows: "JFace is a UI toolkit with classes for handling many common UI programming tasks. JFace is window system-independent in both its API and implementation, and is designed to work with SWT without hiding it."
It includes a whole range of UI toolkit components, from image and font registries, text support, dialogs, databinding, and frameworks for preferences and wizards to progress reporting for long-running operations. These and other JFace UI structures, such as actions and viewers, form the basis of the Eclipse UI.