JavaFX is a name for set of things related to each other:

1) a RIA (Rich Internet Application) framework like Adobe Flex and Microsoft Silverlight
the difference is it is based on Java, instead of flash pluging you need JVM on client
so unlike Silverlight it runs on every OS.
like flash which has its own scripting language JavaFX has its own scripting language
the JavaFX plugin is a Java Application it self that runs JavaFX scripts and provides access to Java API

2) JavaFX script
the scripting language used in JavaFX appplications

3) JavaFX mobile
the JavaFX runtime for JavaME (J2ME) Mobile phones , similar to flashlit

adding to URLs posted by sasan here is WIKI of developers:
http://jfx.wikia.com

and here is the project development site:
https://openjfx.dev.java.net/

I personally like It and I am going to give  it a try at my next project, it feels like return of applets..