What is the Numeraire dollar?

Can you please explain what the Numeraire dollar is? I've heard about it in the context of cryptocurrency and finance, but I'm not quite sure how it works or what makes it unique. Is it a form of digital currency? How is it different from other cryptocurrencies or stablecoins? And what kind of use cases does it have in the world of finance? I'm really curious to learn more about this fascinating topic.