To reset an iPhone, there are two main types of reset: a hard reset (force restart) that does not delete data, and a factory reset that erases all content and settings.

Hard Reset (Force Restart)

• For iPhone 8 and newer (including iPhone X, 11, 12, 13, 14, 15, 16):
  1. Quickly press and release the Volume Up button.
  2. Quickly press and release the Volume Down button.
  3. Press and hold the Side (power) button until the Apple logo appears.
• For iPhone 7 and 7 Plus:
  1. Press and hold both the Volume Down button and the Sleep/Wake (power) button simultaneously.
  2. Keep holding until the Apple logo appears.
• For iPhone 6s and earlier:
  1. Press and hold the Home button and Sleep/Wake (power) button simultaneously.
  2. Keep holding until the Apple logo appears.

This resets the iPhone to resolve freezes or unresponsiveness and does not erase any data.

Factory Reset (Erase All Content and Settings)

• Open the Settings app.
• Go to General > Transfer or Reset iPhone.
• Tap Reset > Erase All Content and Settings.
• You may need to enter your passcode or Apple ID password to confirm.
• Follow prompts to erase the iPhone, which will delete all data and restore factory settings.

If the passcode is forgotten, a factory reset requires putting the phone in Recovery Mode and restoring via a computer with iTunes or Finder.

In summary, the hard reset is used to reboot the iPhone without deleting data, while the factory reset erases everything and restores the device to its original state.