If you've owned and sold at least one iPhone, iPod Touch, or iPad tablet so far, then you've probably known or been advised to delete everything on your terminal / return to factory settings so as not to give your new owner valuable data. You can delete the entire contents of an iPhone, iPod Touch, or iPad tablet using the Erase all Content and Settings option available in the Settings> General> Reset menu of Settings. Activating this function will erase everything in the storage environment of your terminal and will restore the terminal to the factory settings, disabling it at the same time.
The procedure is perfect for cleaning an iDevice before selling it, or to avoid doing a restore in order to get rid of iOS errors or problems, but it is not indicated if you have a jailbroken terminal. Using this procedure in the case of an iDevice that has been jailbroken will make you feel like you have to restore your terminal, all the data in it being deleted in the process. Although an iDevice normally restarts after deleting all content, the jailbroken terminals will no longer start, but will be locked in a boot loop, meaning they will only display an apple on the screen when you try to start them.
Unfortunately, the only way to "restore" an iPhone, iPod Touch, or iPad tablet that was jailbroken before using this procedure is to restore it from either Recovery Mode or DFU Mode. Before concluding, I recommend that you use this option only if you really want to delete everything in your terminal and avoid it in other situations.