. It means to free your iphone by the limitations imposed on it by AT&T , Verizon and Apple. You are bound to use only two networks of the U.S that are AT&T and Verizon. You can only use those apps that are available in Apple app store. There is no doubt that there are many apps available in Apple app store but there are other plenty of cool unauthorized apps that are just made to make your smartphone an awesome gadget. Many people who are iphone users would like to use these third party apps because they come with cool features and some of them are free. Apart from this some would also like to use their iphone with other GSM carrier networks of the world. For all these problems there is one solution iphone jailbreak.
Iphone jailbreak is a technique in which a software application is installed on your computer, and then transferred to your iPhone, where it "breaks open" the iPhones file system to allow you to modify it. After iphone jailbreak you can do everything from customizing the look of your phone to installing third-party applications (such as titles that are not authorized and available in the App Store) and customized ringtones on it. It depends on you that how far you are willing to go. Jailbreaking lets you do even more than that , you can unlock your iphone so you can use it with any GSM carrier other than the one from which you purchased it.
Once you jailbreak your iphone you void your warranty. So you can't rely on AT&T , Verizon or Apple to fix your problems that you encounter. However jailbreaking is not illegal because you purchase iphone and you can do anything with it as long as it's not harming anyone. You can jailbreak your iphone yourself with a jailbreaking software but be sure to purchase a good software.
You can also go online and take the help from experts. There is a website ultrasnow.eu that provides jailbreaking and unlocking facilities. On this site you will find a step by step mini guide to help you through the process of jailbreaking.