First of all jailbreaking is only for Apple products, it is the process one goes through which will allow the installation of illegal third-party applications.
These applications are usually much more useful and cooler than the official Apple apps. These third-party apps allow you to do everything from changing the background and the app icon images. The most common reasons why many people jailbreak their iPhones or iPods is to unlock the phones to different networks and for the popular games.
Jailbreak allows you to get hold of the classic Super Nintendo game emulators which are never seen on the Apple App Store to games which you would normally have to pay for, for free. Jailbreaking your iPhone or iPod opens it up to a whole world of possibilities.
So is it illegal to jailbreak your iPhone?
The short answer is no.
It’s your iPhone or iPod, so what you do with it is up to you, however, if something goes wrong with it and you take it back to Apple and show them your jailbroken iPhone they will most definitely void your warranty.
It is a good idea to create a backup of your original settings through iTunes if you do decide to jailbreak your iPhone or iPod just in case something goes wrong, but if something does go wrong then you can simply go back to your backup. If that doesn’t work then you can hold the home button and power button simultaneously and reinstall the most current firmware update through iTunes.
So Jailbreak away!