How does paper wallet work?
Determine your private key. Write it down on a piece of paper. Done.
It'll 'work' for as long as you keep it hidden from prying eyes, and are still able to read what is written on the paper.
The term has been generalized to convey the concept of affixing a private key - in visible alphanumeric form - upon any tangible medium by any means (e.g., stamped into metal).
Indeed. "Paper" can mean anything from keys stamped in metal to JPG files.
Because I hate having to type keys accurately, I prefer JPGs stored on multiple encrypted microSD chips, hidden in multiple off-site locations.
I do keep an an actual paper wallet at home with a small amount in it, for emergencies like today. Of course I'll still keep the swept wallet. It still has Bcash and Bgold in it.