Can I get a clarification?

Okay I read the flag FAQ and I get most of it. If you don’t know what Swastikas or nudity are, you can always look 'em up.

But this section[SNIP]
goatze, If you don?t know what it is, count yourself lucky, if you do, you know why it is banned, as I recall the posting of the Image is a Immediate IP ban, consider your self warned.
Tub Girl, this is one like the above, see its description, Ditto on it here.
[ENDSNIP]

has me completely stumped.
I have no idea what these refer to.

Ok Goatse is a website with a pic of a dude holding his butthole open wide enough to stuff a Nerf football in.

tubgirl is a big ol fat girl who craps on herself in a bath tub and wallows on in it.

Not the answer you were expecting huh?