Related genres include: Amateur pornography originally referred only to pornography produced by amateurs but now also includes professionally made pornography designed to appear as if it were amateur. Unlike erotic films, pornographic films contain explicit sexuality and do not claim any artistic merit. It is sometimes described as a sexual fantasy, by women or men, depicting an exhibitionist or physique worship scenario. Ass to mouth pornography shows the transfer of a performer penis from a second performer anus to that same second performer mouth in a single shot. Fisting pornography features the insertion of an entire hand into a performer vagina or anus. Saliva pornography involves salivation and saliva. Although interracial pornography theoretically can apply to depictions of sexual activity between performers of any different racial groups, the term is most commonly used for heterosexual sex acts between black and white performers. Pornography is often referred to as porn and a pornographic work as a porno. Group sex is sexual behavior involving more than two gay twinks participants. Mutual masturbation can be practiced by males or females in pairs or groups with or without actually touching another person as indicated by the following examples of contact versus non-contact scenarios: Non-contact mutual masturbation Two people masturbating in the presence of each other but not touching. Lesbian pornography made for women is usually made by women, and usually features women who identify as lesbian or bisexual. As of 2013, little analysis of this paraphilia gay hentai has been reported in medical literature. Another variant of reality pornography consists of normal couples that are filmed by professionals, in which case the only obvious distinction from amateur pornography is the higher quality of production, filming and editing. Entacle erotica describes a type of pornography most commonly porn milf found in Japan which integrates traditional pornography with elements of bestiality and a fantasy, horror, or science-fiction theme.