If you understand Proof-of-Work, you'll see that this is a good way to describe Bitcoin.
Just like with gold, anyone can buy a miner to start digging for it. And it has a property that, IMO, is very important for a currency, which is a fixed limit in the supply. You could go beyond, and say that with Bitcoin you can do much more than with gold, since you can send it over the internet without having to rely on third parties.