They're not actually unique digital images though. They're 'unique' digital receipts to say you've bought the image. You can copy the actual image all you want. Or you could even make a different receipt to say you bought that same image.
And if that makes it sound like you're buying something with absolutely no value whatsoever, then you are correct.
Yes you're correct, I phrased it badly. It's not the digital file itself that is unique, but the ownership right of the 'original' if you want to call it that. What you might call the certificate of authenticity, which proves that YOU own the original item.
Yes in many ways NFTs can be said to be worthless and can be a big scam, but there are potential legitimate uses, such as an artist selling a piece of digital art once, for a high value, and one person owning that original piece, however many 'copies' may exist. In that regard it's not much different to traditional art where multiple copies and prints can exist but only one is the original and that's where the big value lies.
I've still no idea what they are as in what's the point?
Is it a picture?
What is it for?
What does it do?
Why would you want it?
Is it one of these influencer things, where a nobody tells another nobody they should have it and then everyone has one?
It's a collectable. It being an NFT means that they are literally selling ownership rights to the digital artefact - in this case an image, but it can be music or a video or even a tweet. I think the first ever tweet was later sold as an NFT, so someone has the 'pleasure' of knowing that they and they alone now 'own' that tweet, and can sell it on if they want to.
Whether that really means anything is subjective, and like most investments esp in collectables, an item is only worth what someone is willing to pay for it, and that worth can collapse in an instant.
There is a concern that people can get scammed by this sort of thing.