Ok, I have no clue how the toilets work... Is the waste dumped while in the air at all, or is everything done on the ground?

Are there 2 sources of water (one potable, one not), or do they all come from one tank? and if so, is it potable?

(yeah, I know, I've got too much time in my hands to be thinking about this...)

Mods, can you please edit the title to "how do"? thx