I've just dug a hole in my back garden, and created 21 million tiny slices of air that now occupy that space. It took work to dig this hole, so it definitely has value. And I'm only digging one hole, ever, I promise.

I've also made a list of people who own the different bits of air in the hole. I'm using pencil and paper, but it works. If you give me some money I can write your name on there and you can "store value". Later if you tell me to write someone else's name, I can rub yours out and you can "exchange large values".

If you or your friends want the money back later, I can give it to you. Probably... mostly. But don't ask me for more money than you gave me in the first place, because I won't have it.

p.s. I lied when I said I dug the hole by myself. I really dug up a billion tonnes of coal and used it to power a microscopic spaghetti noodle which dug the hole. For some reason this gave a lot of people confidence that my hole is the One True Hole.