Here you can select and deselect whether you want to use Face ID for:
- iPhone Unlock (to unlock your iPhone from its unlock screen)
- iTunes & App Store (for any purchases in iTunes or Apple App Store)
- Apple Pay (if you have Apple Pay set up, you can use Face ID to pay for certain items)
- Password Autofill (Face ID will be used to verify your identity to autofill passwords at various websites)
Choose which options you want to use Face ID and which you'd like to turn off.