In system settings, you can edit, for example:
Accidents may happen and your phone may stop responding. You can restore the original factory settings, but be careful, since this reset removes all data you have saved in the phone memory and all your personalization.
If you are disposing your phone, note that you are responsible of removing all private content.
You may need the have the security code to restore the original settings. To reset your phone to its original settings and to remove all your data, on the home screen, type in *#7370#.