Start with the man pages. Running the command man followed by a space and then followed by the command you’re using will almost always give you a man page of the basics of how that command works. The fstab has its own man page too. An internet search “man fstab” or whatever command you’re interested in should also net many mirrors of the those man pages as well.
The top half is drawn completely different (looking like a classic far side) than the lower shaded half (looking more like an old cartoon). I’m sure the difference in drawing style has something to do with the joke, but I’m not sure how.