Quoted:
Forgive my ignorance but what does "jailbreak" mean? Ditto the terms "tethered" and "untethered". I don't have a smartphone.
Jailbreak is to open the phone up to developer level access to tweak and install programs Apple does not want you to make.
Tethered means if jail broken you need it connected to your computer whenever you reboot it as it needs assistance from the computer to finish the reboot cycle.
Untethered means you will be able to reboot it without benefit of being connected to the computer with the jailbreak program running.
If the battery dies on a jail broken phone that needs to be tethered to reboot, you're basically fucked until you can get to a computer with the needed program on it.
Untethered is the only way it makes sense for me.