This week's book giveaways are in the Refactoring and Agile forums. We're giving away four copies each of Re-engineering Legacy Software and Docker in Action and have the authors on-line! See this thread and this one for details.
It's just a flag in the Thread object. The JVM will continue to run only as long as non-daemon threads exist. As soon as the only running threads have the daemon property set, the JVM will exit. That's it -- nothing more.