JavaFX is Java's modern GUI framework. It offers a streamlined, yet powerful way to create graphical user interfaces. Its central metaphor is that of a stage and scene. Loosely speaking, a stage defines a space and a scene defines what goes in that space. Or, put another way, a stage can be thought of as a container for scenes, and a scene can be thought of as a container for items that comprise the scene.
As you are probably aware, the modern world demands dynamic, visually engaging interfaces. JavaFX makes it easy to add that "visual sparkle" to your applications. This can be achieved, for example, through the use of effects, transforms, and animation. In my view, JavaFX's support for animation – especially its ability to animate 3-D objects – is one of its most impressive features.
One last point: Having used several different GUIs in my programming career, I find JavaFX to be extraordinarily clear, consistent, and easy to use.