So what do the letters for each drive / disk / etc mean (D:, E:, Q:, C:; etc)
the letters themselves mean nothing, but each drive must have a letter
and it only applies to windows. other operating systems don't do this exact thing (but they do, of course, have other names for drives)
the main drive is usually C:
I'm not sure if that's required or just a seriously common convention, but if it's optional, changing it would probably break badly-written software