I’m working on a long blog post this week that will be pubbed in a few places. And the question of porn and erotica came up.
I have my own definitions for both. But I’d rather post the wiki definitions right now.
And, keep in mind there is always going to be someone who doesn’t agree, not even with these definitions. Sarah Palin’s daughter’s ex-boyfriend, what’s-his-name, posed partially nude for a Playgirl and Ms. Palin called that porn, which I found interesting because there wasn’t even full frontal nudity.
Erotica: Erotica and pornography
The Naked Maja (c. 1800–1803) by Francisco de Goya.
Distinction is often made between erotica and pornography (the depiction of acts in a sensational manner so as to arouse a quick intense emotional reaction) (as well as the lesser known genre of sexual entertainment, ribaldry), although depending on the viewer they may seem one and the same. Pornography’s objective is the graphic depiction of sexually explicit scenes. Pornography is often described as exploitative or degrading.
Here’s the link.
Pornography or porn is the portrayal of explicit sexual subject matter for the purposes of sexual arousal and erotic satisfaction.
Pornography may use any of a variety of media, ranging from books, magazines, postcards, photos, sculpture, drawing, painting, animation, sound recording, film, video, or video game. However, when sexual acts are performed for a live audience, by definition it is not pornography, as the term applies to the depiction of the act, rather than the act itself. Thus, portrayals such as sex shows and striptease are not classified as pornography.
A pornographic model poses for pornographic photographs. A pornographic actor or porn star performs in pornographic films. In cases where limited dramatic skills are involved, a performer in pornographic films may be called a pornographic model.
A distinction is often made between erotica (the portrayal of sexuality with high-art aspirations, focusing also on feelings and emotions) and pornography (the depiction of acts in a sensational manner, with the entire focus on the physical act, so as to arouse quick intense reactions). 
Pornography has often been subject to censorship and legal restraints on publication on grounds of obscenity. Such grounds and the very definition of what is or is not pornography have differed in different historical, cultural, and national contexts.
With the emergence of social attitudes more tolerant of sexuality and with more explicit definitions of obscenity in law, an industry for the production and consumption of pornography arose in the latter half of the 20th century. The introduction of home video and the Internet saw booms in a porn industry that today generates billions of dollars a year worldwide.
And here’s the link to this one.