Porn is an abbreviation of pornography, a type of movie, magazine, book, or website that features sex or sexual situations with no other redeeming features.
Porn is different than erotica, which may also feature sex but has more artistic merit. And it's different from a mainstream movie with a few sex scenes. Supreme Court Justice Potter Stewart famously said about porn, "I'll know it when I see it." People can also use the word porn to describe anything singular in focus that's meant to stir the senses: food porn, for example, features endless, excessive pictures of amazing looking food.
