From NetBeans Platform :
The NetBeans platform is a common platform for Swing applications. It provides “plumbing”, before which each developer must write himself down - saving state, connecting actions to menu items, toolbar elements and keyboard shortcuts; window management, etc.
This is an API built with Swing, which is supposed to provide some additional “built-in” functions. Since you need to know Swing in order to be able to use it. I suggest you focus on Swing for now.
source share