The JailbreakMe app is a Web-based app used to jailbreak products such as the iPhone and iPad. Jailbreaking an Apple product gives the user access to third party apps at the Cydia app store that aren't found in the official App Store.
The apps available for download in Cydia grant much greater control over an iPhone or iPad's performance. For instance, users can tweak a device's visual layout completely by adding a theme to it. They can also download a new set of system sounds.
The JailbreakMe application is only one of several methods available for users to jailbreak their phone. What initially distinguished JailbreakMe from other methods of jailbreaking is that it exploited a flaw in the Safari Web browser that let users jailbreak devices in a matter of minutes using Wi-Fi or a cellular network. Other methods typically require users to plug the device into a computer.
Apple fixed the flaw in Safari with the release of iOS 4.3.3. The JailbreakMe application has so far been unable to find any new flaws to exploit, making it a very outdated method for jailbreaking an iPhone or iPad. However, the application is still available and free to use for devices running old operating systems.