Would have been better to link to the repo [1] directly.
The repository contains the materials of a class, so without attending the class or having a rather strong pre-existing knowledge about hypervisors on x86-x64, the material is going to be very hard to follow.
From my PoV, there are definitely better (as in, explained with a lot more details) tutorials online on how to start your hypervisor from scratch which I'd recommend before trying to understand this one (which has some really nice peculiarities such as Fuzzing UEFI with code coverage).