High heel pornography involves women or men dressed in high heeled shoes. Often a dominant woman, she may be called a Dom, Domme /ˈdɒm/, Femdomme, Domina, or Dominatrix, depending on context or personal preference. When sexual activity is centered on one of the threesome, then the activity may be described as a gang bang of the person. Sex experts gay videos have praised various techniques that the performer can use during fellatio to increase their partner pleasure. 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. Some productions are noted for sophisticated and/or experimental storytelling and animation techniques. A variation on this is to place the fingers and thumb on the penis as if playing a flute, and then shuttle them back and forth. An orgy is a gathering where guests freely engage in open and unrestrained sexual activity or group sex; and a bunga bunga orgy is an orgy in which participants have sex underwater, such as in a swimming pool or a hot tub. Can also include auto-fellatio, or performing oral sex on oneself. A crush fetish is a fetish in which one is sexually aroused usually when someone crushes objects, food, and sometimes small animals with their body, usually under their foot, or when crushed oneself. Group sex is sexual behavior involving more than two participants. BDSM is a variety of erotic practices involving dominance and submission, role-playing, restraint, and other interpersonal dynamics. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. When he is in position the cover is closed. Interracial pornography typically employs ethnic and racial stereotypes in its depiction of performers and many of interracial pornographic films still include racial stereotypes, although the segregation of actors by race has diminished considerably.