1. Zero-knowledge proofs actually are a form of proof, just not mathematical/philosophical proof by deductive argument, but rather proof in the sense of "I can prove I have this power", in the everyday sense.

2. They also are "zero-knowledge" in the sense (the technical, specialized sense) that they don't spill knowledge of your secret key or whatever. And that's useful, and we might as well call that "zero-knowledge", sure why not.

3. Zero-knowledge proof actually is a useful technique for various things. The things it was designed for, mostly.

4. A friend of mine opines that when he hears someone say "zero-knowledge", he likes to imagine they just mean "ignorance", and that makes such statements as "this system is powered by zero-knowledge" funny.

5. Actually, I did watch this video https://www.youtube.com/watch?v=Otvcbw6k4eo and found it informative about ZK (that's how the cool kids are writing "zero-knowledge" these days), although you will have to muse over the implications of the video yourself, ime. So, I guess I actually know a fair amount about zero-knowledge (← oxymoron?).