www.chinaphonearena.com

From what I gather:

Actual physical Micro-SD card is this:
/storage/sdcard0 == /mnt/sdcard (shortcut) == /sdcard/ (shortcut)

Internal memory is this:
/storage/sdcard1 == /mnt/sdcard2 (shortcut)

Is this true? I'm pretty new to the whole Unix filesystem as a whole and find myself pretty confused.

It will depend on the ROM. Generally it's as you said. You should be able to look in ES Explorer or similar and it will show the exact paths.