As far as I understand, it's a modified/extended version of Wine, which, as the name suggests, is not an emulator (but rather a userspace reimplementation of the Windows API, including a layer that translates DirectX to OpenGL/Vulkan).

The reverse, i.e. running Linux binaries on Windows or macOS, is not easily possible without virtualization, since Linux uses direct syscalls instead of always going through a dynamically linked static library that can take care of compatibility in the way that Wine does. (At the very least, it requires kernel support, like WSL1; Wine is all userspace.)