To turn this thread back to its topic, I would personally distinguish between the erotic, erotica, and pornography.

What is erotic, is, as said before, entirely a personal matter. Some people find some quite strange things erotic.

"Erotica" is a useful term for pictures that are intended primarily as artworks, but which deal with sexual themes.

"Pornography", to my mind, is something for which the degree of sexual titillation is the only thing that counts. There is no attempt at artistic quality. (I am aware that some would not agree with this definition.)

The distinction must be made, otherwise one concludes that there are subjects that cannot be treated by the artist, which to me is an abhorent conclusion. It is terrible to say that some subjects are "suitable for artists" (flowers, butterflies, etc) and others are not (sexual acts). And I don't see any great reason why the subject cannot be discussed politely here. It would be against the ToS to post a graphic description of a sex act, but not to write that people do, in fact, have sex..