Sorry, that's what you get when you read roseindia tutorials. I don't recommend going there.
I don't understand your reason for criticizing roseindia tutorials.
that's the purpose of making a thread a daemon thread; a running user thread will prevent the JVM from exiting whereas a running daemon thread will not
The purpose of making a thread a daemon thread is to use it for background supporting tasks. A daemon thread is a service provider for other threads running in the same process. For example, the print spooler is a daemon thread that runs in the background and loads printing jobs (created by user threads) into a buffer (a special area in memory) where a printer can access them when it is ready.
The Java Virtual Machine exits when the only threads running are all daemon threads because there are no running user threads to service.