What exactly is the difference between screen -x and screen -r. I know they're both for reattaching to the screen, but not sure I grasp when to use one or the other.
-r attaches a detached session, while -x attaches an attached session without detaching it, so it runs in both the places at the same time. Another useful option combination is -d -r which detaches a session if needed first and then reattaches it.