Pornography–"porn" or "porno" for short–is material that depicts nudity or sexual acts for the purpose of sexual stimulation. However, the presence of nudity or sexual acts in piece of media does not necessarily make that media pornographic if the purpose of that media form is something other than sexual stimulation. Pornography can take the form of photographs, videos, written material, audio recordings, or animation, among other media formats.
The legality of pornography varies from country to country. In the United States, generally people can purchase or access pornographic materials legally. That being said, it is illegal to knowingly distribute pornography to minors under 18 U.S.C. §1470. Further, under 18 U.S. Code § 1466A, it is illegal to knowingly produce, distribute, receive, or possess pornography with the intent to distribute if said pornography depicts minors in a sexual act. Revenge porn–where sexual media of someone is distributed without that person’s consent–is also illegal in all but four states.
Further guidelines on United State federal law in regards to obscenity can be found here on the Department of Justice website. A guide to pornography laws in some other countries can be found here.
[Last updated in July of 2020 by the Wex Definitions Team]