There seems to be quite a bit of dispute on DeviantArt over the differences between the three artistic genres mentioned in this article's title. Some think Whatever by So-And-So is a nude, while others insist it's porn, while more still think it's erotica, and a few think it's all three. Well, I did a bit of research, and I'm here to tell everyone who's reading this that these three are, in fact, different categories of art. How, you ask? Let's take a look.
1. Artistic Nudes
"Nudity in art has generally reflected with some exceptions social standards of aesthetics and morality of their time in painting, sculpture and more recently in photography." (wikipedia.org)
"A type of photo in which a model appears to be nude or partially nude, where the intent of the image is artistic expression (as opposed to marketing, viewer arousal, etc.). Not exclusive of other photo types (eg, a photo could be artistically erotic)." (just-stuart.com)
"Artistic nudity is a form of nudity that is intended to showcase the body as art. Artistic nudes are tylically suitable for framing and exhibition." (eleganteye.com)
The above quotes describe this legitimate artistic genre. The last quote states the key factor that differentiates Artistic Nudity from the other two genres: Artistic Nudity is intended to depict the body as a work of art, and also sometimes to display the artist's skill in anatomical accuracy or study. Its purpose is never to arouse or excite, therefore one can infer that photographic Nudes would never be digitally edited to look particularly appealing.
Artistic Nudes, unlike Erotica and Pornography, are usually appropriate to display in such places as a high-school art class or public museum. Online, they would most likely not be labeled as "NSFW."
"Eroticism is an aesthetic focus on sexual desire, especially the feelings of anticipation of sexual activity. It is not only the state of arousal and anticipation, but also the attempt through various means to incite those feelings." (wikipedia.org)
"A work featuring love and sex between characters, but not considered pornographic." (public.clunet.edu)
Like Nudity, Erotica is a legitimate artistic genre, focusing on actual aesthetic technicalities. However, unlike Nudes, Erotica is intended to portray and induce feelings related to sexual desire, thereby treating sexual desire as an "emotion." A work of Erotica is really no different from a particularly happy-, sad-, or angry-looking piece; the difference is just what emotion is being portrayed.
Erotica would not be appropriate in an educational setting, but may be okay for a particular wing of a museum. Online, it would probably be considered NSFW.
"Pornography or porn is the portrayal of explicit sexual subject matter for the purposes of sexual excitement and erotic satisfaction." (wikipedia.org)
"A work featuring graphic/explicit sex between characters." (public.clunet.edu)
"...sometimes shortened to porn or porno, is, in its broadest state, the explicit representation of the human body or sexual activity with the goal of sexual arousal and/or sexual relief."(blogs.sfweekly.com)
Pornography is not an actual artistic genre or movement. It's the technical term for, in laymen's terms, "generic fapping material." It may or may not posses any actual artistic merit, and if it does, the skill isn't what's being focused on. In photographic Pornography, photo-editing software is often used religiously so as to enhance the subjects to the peak of sexiness. Fetish-art falls under the category of porn, as does hentai.
Pornography is never appropriate to show anywhere in public (except perhaps at certain enthusiast-conventions) and is always marked as NSFW online.
Now that you know the differences between these not-so-similar categories, you can judge for yourself whether or not that one questionable picture you've been pondering is really a work of art. You can find examples of each of these genres in the Artist's Comments. Thanks for reading!