[Walf]

Not quite. Programs normally need to be compiled per system type, and sometimes per system, due to differences in the OSes' versions, APIs and hardware. The idea behind this type of emulator is that you need compile it only once, and the emulator takes care of those differences for you. The Bedrock program would always ‘see’ the same OS and hardware.

[benbridle]

You've got it, yeah. It makes writing programs across different systems so much nicer, because you can just write your programs against a single tidy 'bedrock' abstraction of the file system, screen, networking, etc.