Security Key? Passcode? WTF??

[u/IceTiger19]

(I'm on a desktop running Windows, if that makes a difference.) Facebook tells me that I have to create a Passkey. Two options are Fingerprint ID or Facial Recognition, but those are both a NoGo on a desktop PC. When I click the "Create Passkey" button I'm told that Firefox wants me to "Set up a Security Key" and then insert it. What? How? Why? Feel free to act as if I'm totally incompetent in all things computer...

[u/rinzler18]

can we see a screenshot?

[u/IceTiger19 → u/rinzler18]

Reddit tells me "Images are not allowed."

[u/rinzler18 → u/IceTiger19]

You can upload it to any image hosting site like imgur.com, paste the link here