Understanding the boot loader

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I'm trying to figure out how the boot loader works, and it seems to me that it consists of two files boot.img and core.img.

Can someone confirm that that is the case?

Yes. Look in the Linux version VentoyWorker.sh in the tool folder (looks like Windows does all the work inside of the .exe so you can't see it there) and ctrl+F for core.img and boot.img

You can find where it puts boot.img into the mbr and core.img into the 1MB space at the beginning of the disk before the first partition.