Java classes are organized into packages, which belong together in some way. The core classes are packaged in the java.* pages. The most important ones are the java.lang package (e.g. Object, String), the java.io package, and the java.util package.
Java contains an Abstract Windowing Toolkit (AWT) for creating basic graphical user interfaces (GUIs). The classes for implementing AWT-based GUIs are contained in the java.awt package.
However, AWT has only a limited scope. This is the reason why Swing has been developed for creating desktop applications. The Swing classes can be found in the javax.swing package (javax means "Java extensions").
Perhaps suns 'java desktop' is meant here. AFAIK it's more or less a collection of applications, running on a linux-system, perhaps meant to be the realization of the 'thin client' or 'net box' or something. Maybe I'm pretty wrong...
I like linux, and I like java - but I don't like the idea of a java-desktop.
the latest news says Sun's Java Desktop (or better known as Java Enterprise System (JES) is offered not only in Solaris, Linux, but Windows and other *nix. They charge 100 bucks/ per user/ per year though.