It’s basically Wine with a custom D12 translation to Metal calls. Right now it’s not really intended for end-users so the experience involves a lot of steps that aren’t consumer-friendly, but some folks are publishing wrappers that simplify the process.

I imagine that in the future, something like Steam will wrap this functionality to provide the ability to run the whole library under the toolkit. And individually-published games will do the same so they install and run with a more consumer-friendly experience.