This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Basically, green threads are JDK-provided threads and native threads are OS-provided threads. In clear, if your JVM uses green threads, there will only be one process as far as the OS is concerned, and the JVM is responsible for simulating the different threads of your application within its own thread. If you use native threads, there will normally be one OS process per thread in your application. Worker threads are just threads you use to carry out some task, kind of like,...,well, a worker thread Read a little more about that here: http://developer.java.sun.com/developer/qow/archive/97/