While bondage is a very popular variation within the larger field of BDSM, it is nevertheless sometimes differentiated from the rest of this field. Pornography can be classified according to the physical characteristics of the participants, videos gays fetish, sexual orientation, etc., as well as the types of sexual activity featured. It is also often mixed with other fetishes in practice, such as voyeurism, denial, etc. Anal sex or anal intercourse is generally the insertion and thrusting of the erect penis into a person anus, or anus and rectum, for sexual pleasure. In straight pornography, intercourse is often followed by a facial, pearl necklace or other visible ejaculation. It may be used as foreplay, or as an alternative to sexual penetration. Fetish cuckolding can have a wide range of expression, from pillow-talk fantasy between monogamous partners to extreme alternative lifestyles, depending on the couple. In pornography, depictions of lesbian sex form a popular subgenre, directed toward a male heterosexual and female homosexual audience. Squirt pornography involves women ejaculating. Bukkake videos are a relatively prevalent niche in contemporary momporn pornographic films. Sub-genres of Japanese porn Among the various sub-genres of Japanese pornography are the following: Lolicon ロリコン: This genre involves prepubescent and adolescent girls between the aged of 6-12. An orgy is a gathering hentai sex 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. It explores the more mental aspect of BDSM. It is sometimes described as a sexual fantasy, by women or men, depicting an exhibitionist or physique worship scenario. Pornographic films are generally classified into sub-genres which describe the sexual fantasy which the film and actors attempt to create. Jail/Prison/Police pornography involves people in police custody or inmates in jails or prisons in various sexual situations, such as strip searches or body cavity searches.