Hello Nairalanders please I am bit confuse about the lavafx. I WILL LIKe TO know the kind of apps I can develop with lavafx. Thanks

You can use JavaFX for all the kind of apps you can create with Java Swings but with the advantages that JavaFX brings to bear:
1. JavaFX provides a cleaner architectural structure compared to Swings.
2. Instead of Layout managers in swings JavaFX uses nodes giving you a upper hand in laying out your UI components.
3. JavaFX has improved events handling.
4. JavaFX has support for Properties, hence much easier to trigger UI events when a property changes.
5. it much more easier to build custom controls with JavaFX.
6. JavaFX is skinnable with it's support for css.
7. It has special effects.
8. It has support for animations.
9. It enables a app-like installation on the client side, without any prerequisites.
10. It provides the possibility of developing up-to-date user interfaces with animations, multitouch, and the like.
11. It's simpler to create sleek professional looking apps like this compared to swings.
12. JavaFX is a successor to Swing, there every possibility that swing might be faced off eventually (but, who knows when ?)
13. JavaFX is the equivalent of Microsoft Windows Presentation Foundation (WPF)

The source code for the above app is made available at http://www.captaincasa.com/ for educational purpose.

Thanks very much Kudaisi. Just this question. (1) On which device can my javafx app run on.? (2) Can I develope a ".apk, .exe, .jar" app with javafx?

Porting for android is possible (and ongoing) but not necessary. I advice to restrict yourself to only using JavaFX where you would use Swing app (i.e Desktops...jar, exe or web applets..)