Whai is jailbreaking???

Jailbreaking is basically modifying the iPhone's firmware so that you can get access to the internals of its operating system and install a whole slew of third-party applications on your iPhone that are not otherwise available through official channels (ie, the App Store). Jailbreaking your iPhone in and of itself doesn't normally make much difference in your operation of it, but it does allow you to install other third-party applications that are not blessed by Apple. This is a double-edged sword, however..... The upside is that there are some useful and interesting applications available through unofficial channels that will likely never appear on the App Store due to SDK restrictions. For example, Apple's official position is that applications are not permitted to continue to run in the background on the iPhone. This restriction is not because the iPhone can't run apps in the background, but merely because Apple did not want developers doing this. Further, applications the hack or extend the functionality of built-in iPhone apps like Mail and Safari and the phone app are not permitted by the SDK, yet unofficial apps have no such restrictions. The downside to this approach is that although there are some brilliant developers out there in the jailbreak community, these folks are all flying by the seat of their pants when it comes to writing these apps..... They have no official support from Apple, and are building most of these apps by reverse-engineering the existing iPhone OS and built-in applications to figure out how things work so they can build their own apps. This means that the quality of many of these jailbreak apps, particularly those that act as system extensions, is extremely dubious. They're doing things the iPhone may not have been designed to do, and certainly doing them without any official blessing from Apple.