It's a card with black-and-white artwork printed as a traditional foil using a special silver substrate, then finished with a glossy varnish like the showcase eternal night cards you already know from Innistrad: Midnight Hunt and Innistrad: Crimson Vow
For example, a given property may or may not have elves, and this type of worldbuilding impacts reprint selection
Lotho, Corrupt Shirriff Marcy: First, can I say that I really, really hate trying to type the word 'Shirriff'
It's a pretty simple concept that opens up a lot of different lines of play once you start to get the hang of the basics of the game, but at the same time, none of these cards are so overly complex that they're too daunting for beginners like myself
There are notable costs to the card too though, and as a result Unsubstantiate is the card Im least sure on the numbers for