How does the facial search engine pimeyes work?

It's frighteningly accurate. I've tested on pictures of people I know and it's accurately found other pictures of them online which leads to their identity. The false positive rate is pretty low.

I have a technical background (although not CS), so please provide more than a simple response if you can.

Thanks.

Dumb question, but how do I know chatgpt is not just copy/pasting from the web?

Tried chatgpt for the first time. Seems cool. Dumb, question, but how do I know it's not just copy/pasting something a person wrote on the web?

I ask it for a recommendation for speakers. Gives a good reply. It seems to me it could've just done a web search and then copied what someone wrote on the web as a reply.

Is there a way to test/use chatgpt to prove to myself that it's not just copying and pasting from the web?