Cydia Impactor cydia tweak removes and reverts all changes made to the device and returns it to “stock” iOS software without updating to a new version of iOS.
Running this tool will destroy all of your data: this is, in fact, the goal.
After the tool finishes, damaged/lost files will be repaired (back to Apple stock) and the device will no longer be “jailbroken”.
There are two main reasons someone might want to do this:
You should make a backup first. After using this tool, you will have to re-activate your device. If you are logged in to iCloud, you will need to have your Apple ID password to get access to your device after it reboots.