Today, pornographic films can be sold or rented on DVD, shown through Internet and special channels and pay-per-view on cable and satellite, and in adult theaters. As a form of non-penetrative sex, it can be done for its own enjoyment or as foreplay. These actors often play the top roles but this is not always the case, such as with Kristen Bjorn and some Bel Ami models. As well as traditional attraction, the young gay porn topic also incorporates feederism and gaining, where sexual gratification is obtained via the process of gaining body fat. Boots are seen as the perhaps most fetishistic of all footwear and boots may be the most popular fetish clothing attire. The introduction of the home video and Internet saw a boom in the worldwide porn industry that generates billions of dollars annually. The initialism BDSM includes psychological and physiological facets: Bondage & Discipline Dominance & Submission Sadism & Masochism Types of Play This model for differentiating among these three aspects of BDSM is increasingly used in literature today. The term comes from the French voyeur, one who looks. Nevertheless, it is only an attempt at phenomenological differentiation. A bisexual threesome may involve a man having sex with a man and a woman, the woman having gay hentai sex with a man and a woman, or all three having sex with each other. Erotic spankings are commonly combined with other forms nude milfs of sexual foreplay. The slave is usually strictly forbidden from placing their lips directly on the body of the dominant so the practice routinely involves them receiving much of the spray all over their face, hair and body, however, another way of doing this that applies mostly to male dominants, is to place the mouth on the head of the penis and drink the urine as it is released. In the 18th and 19th centuries, some European theologians and physicians described it as heinous, deplorable, and hideous, but during the 20th century, these taboos generally declined. Reality and voyeur pornography, animated videos, and legally prohibited acts also influence the classification of pornography.