What? Why? How? Answers to these questions, AND MORE, in Gizmodo's ultimate jailbreaking guide for iPhones, iPods and iPads.
...freedom for iOS users, giving them a way to break free from Apple's restrictive App Store ecosystem, install whatever software they want, and use their phones however they please. Technically, each jailbreak is a hack; an exploitation of some flaw in the devices' operating systems, used to install unauthorized software. This software generally includes some kind of alternative App Store, called either Cydia or Rock.
Jailbreaking is openly discouraged by Apple, who updates various jailbreak exploits out of existence as fast as hackers can find them, but even after three years of pressure from Jobs and Co., the jailbreak scene is still as lively as ever.
...and worth trying because...
...the jailbreak app stores are packed full of previously forbidden goodness. This ranges from replacement text message apps and device skins to Wi-Fi tethering apps and access to hidden device settings. The best case to be made for jailbreaking is a showcase of the apps it lets you download.
Here are some of the best apps for iPhone and iPod:
...and for iPad:
...and is easy to install on any iOS device
There are a few different options for jailbreaking iOS devices, some more involved than others, but at this point, and for current software versions LimeRa1n is the best choice. It works the same way on both Windows and Mac, works for nearly all iDevices (though some 2G iPhone owners have problems), and gets the job done quickly.
• An iOS device running version 3.2.2 (iPad) or 4.1 (iPhone and iPod Touch)
• A computer with which your iDevice has been paired via sync
• LimeRa1n software from here (an .EXE for Windows users, and a .APP file for Mac users, which must be extracted from a .ZIP)
• A recent iTunes backup of your device, since it will need to be restored after jailbreaking
• About 10 minutes, max
1. Connect your iDevice to your computer, and wait until it is recognized by the operating system or iTunes
2. Open the LimeRa1n app
3. Click "make it ra1n"
4. Your device will enter recovery mode. One it's done, you will be prompted to manually put the device in DFU mode by pressing and holding your home and power buttons.
5. After about 10 or 15 seconds you'll need to release the power button, but continue holding the home button. You will be prompted by the installer to perform this step, so keep a close eye on it.
6. The device will enter DFU mode, at which point you can let go of the home button. The installer takes care of the rest.
When the phone reboots you will see a new startup screen, and find a limera1n app on your homescreen. Run it to install Cydia—then from there, whatever the hell you want.