Lot of questions there, the answers to which are fairly straight-forward, if you had spent more than five minutes before posting here.
Bob, the sarcasm isn't appreciated. I know how Favorites work, and I wasn't asking anything about that.
My confusion was because "Good" isn't showing me the roms I actually have. The list is close, but there are some games missing from it whose roms I have, and whose audit passes with no errors. This may be due to the way I store my roms ('non-merged'). I'll do some research and see if I can figure out what's going on.
It helps to know that 'Good' means 'Exists On My Hard Drive', but this raises a new question - if MAME OS X goes to the trouble of figuring out what roms I have, then why should it bother showing me a list of all roms it supports? Like, if I don't have Mappy, then why would I want to see a list containing Mappy that would let me try to start Mappy? Why would anyone ever want to use the 'All' list instead of 'Good'?