What is Tethered Jailbreak
What is Tethered Jailbreak?
Tethered jailbreak is a jailbreak which need a computer everytime your iDevice reboots. Why do you need computer? Because you have to run a program which created to turn-on your iDevice again. You will need to do this everytime the iDevice restarted (after install app), powered off, or when your iDevice battery dies. You have to connect the device to computer, re-run the program, then you may use the iDevice as normal again.
By doing so, you will not loose the jailbreak, data, or any modifications on iDevice, you just need to run the program to make your device started normal again.