...to add my voice, as a retrocomputing enthusiast, because of that and because I dang well can :P
PCMCIA (which is 16-bit) is adapted from ISA. CardBus (which is 32-bit) is adapted from 32-bit PCI. (Yes, Virginia, there *is* 64-bit PCI... it's called PCI Extended aka PCI-X, and is *not* the same as PCI Express aka PCI-E.) CompactFlash is adapted from IDE. I've never heard of any PCMCIA<->CompactFlash interoperability that didn't need a translator ("bridge") chip in between. "PC Card" refers to *both* PCMCIA and CardBus at once, because people these days are brought up too badly to remember a five-letter freakin' acronym, and all three names (and both standards) were from the same committee/commission/group, which was *also* named PCMCIA. Past tense here, because in 2009 it became part of USB just to confuse everyone even more. CompactFlash, on the other hand, is SanDisk's baby.
Also, PCMCIA is not interoperable with CardBus, electrically and (due to the connector notching, which is upside-down from one to the other) physically. If you don't see the little gold stripe near the connector, you have either a 16-bit PCMCIA card or a *really* early (or equally cheap!) 32-bit CardBus card. Chances are pretty high that it's the former and not the latter.
The XT Bus is 8 bits only, and is *very slightly* different from 8-bit ISA (please don't ask, I don't remember the specifics offhand). I would *assume*, although I don't actually know, that the AT Bus and ISA-16 are similarly slightly different. Oh, yeah... if you just say "ISA", you're probably thinking of ISA-16, which was rather a bit more popular. There is 8-bit-only ISA, just ask half the slots in my old 386 ;) Before anyone strikes up an argument, I *do* have a PC-XT clone in addition to the previously-mentioned 386 (which was my first computer, three rebuilds ago), so I'm in a position to know about buses... I need to burn a BIOS chip for it because known-good floppy drives don't work in it right now... haven't gotten around to that yet, though, mostly because UV erasers for EPROMs are relatively expensive at my income bracket.