A PIN is always the backup, not a replacement
Windows Hello does not remove your PIN or password -- it sits alongside them, so if face or fingerprint recognition ever fails, you can always fall back to the PIN you registered.
The biometric data never leaves your device
Face and fingerprint data used by Windows Hello is stored and processed locally on a secure part of your device rather than uploaded anywhere, which is part of why it is considered more secure than typed passwords.
Frequently Asked Questions
What if my computer does not have a camera or fingerprint sensor?
Facial recognition requires a compatible infrared camera and fingerprint recognition requires a physical sensor built into the hardware -- if your device does not have either, those options simply will not appear under "Sign-in options."
What happens if face or fingerprint recognition fails to work?
You can always fall back to signing in with the PIN or password you set up alongside it, so you are never completely locked out.