Should I be afraid?
A little bit, it is one of the more serious issues that Apple has had with macOS. Anybody who has physical access to your Mac or can get to it through via screen sharing, VNC, or remote desktop can gain complete access to the machine.
What is Face ID and is it any good?
Face ID replaces Apple's fingerprint tech (Touch ID) to unlock your iPhone and approve certain actions. It takes a little getting used to and you will find yourself going for the non-existent Touch ID button at first.
Cloud storage services sync folders on your computer to the cloud; allowing you to work from a folder across devices. If you accidentally delete a file sometimes these services even have a recovery feature. This of course only works for files that are in the synced folders.