What can TianoCore's DUET be used for in a PC?

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http://superuser.com – I've recently become interested in DUET, Intel's UEFI emulator for developers. I'm reading that it can be installed to a hard disk, but what does this make it? Some kind of boot monitor? A virtual machine? Would I be able to make BIOS computers run like EFI computers? Could it be used for a software-based secure boot? (HowTos)