It's a semi-untethered jailbreak, to use iPhone terms. The jailbreak doesn't go away when you put it in rest mode, and you can save the exploit in your browser's cache and run it without a network connection. But it does have to be re-run every cold boot.
Also like iPhone jailbreaks, you can't downgrade your system and new jailbreaks take a while to be released publicly after patches come out. Currently the latest is for 5.05