There are two classes of jailbreaks available for iDevices: tethered and untethered jailbreaks.
An untethered jailbreak is the normal, most popular option for jailbreaking your device. As already explained, the only difference you will see in your device is a new app store called Cydia. Untethered jailbreaks take a little longer to be released than tethered Jailbreaks.
A tethered jailbreak, on the other hand, requires more maintenance and upkeep. Think of tethered jailbreaks as the “trial run”, and untethered jailbreaks as the final product. As with all trial software, it works, but comes with a few limitations.
While an untethered jailbroken device can be powered on exactly like a normal iPhone, iPod touch, or iPad, a tethered jailbroken device requires you to plug your device into a computer every time you turn your device completely off (either by the battery dying or if you need to restart). If you attempt to power your device back on without plugging it into a computer, your device will show an Apple logo on the screen until you plug it in. For this reason, tethered jailbreakers must be prepared to be very conscious of their devices battery level, and remember not to restart their device without a computer on hand. Although this may seem inconvenient, it is a good option for those who don’t want to wait for the untethered jailbreak to come out.