Pornographic films are motion pictures with the purpose of promoting sexual arousal in the viewer, often featuring depictions of sexual activity. They appeared shortly after the creation of the motion picture in the early 1900s. Pornographic films have much in common with other forms of pornography and erotica. Pornography is often referred to as "porn" and a pornographic work as a "porno." Older names for a pornographic movie include "adult film," "stag film," and "blue movie." In general, "softcore" refers to pornography that does not depict penetration or "extreme fetish" acts, while "hardcore" refers to pornography that depicts penetration and/or extreme fetish acts.