Anal sex or anal intercourse is generally the insertion and thrusting of the erect penis into a person's anus, or anus and rectum, for sexual pleasure. Other forms of anal sex include fingering, the use of sex toys for anal penetration, oral sex performed on the anus (anilingus), and pegging. Although anal sex most commonly means penileanal penetration, sources sometimes use anal intercourse to exclusively denote penileanal penetration, and anal sex to denote any form of anal sexual activity, especially between pairings as opposed to anal masturbation. While anal sex is commonly associated with male homosexuality, research shows that not all gay men engage in anal sex and that it is not uncommon in heterosexual relationships. Types of anal sex can also be a part of lesbian sexual practices. People may experience pleasure from anal sex by stimulation of the anal nerve endings, and orgasm may be achieved through anal penetration – by indirect stimulation of the prostate in men, indirect stimulation of the clitoris or an area of the vagina (sometimes called the G-spot) in women, and other sensory nerves (especially the pudendal nerve). However, people may also find anal sex painful, sometimes extremely so, which may be due to psychological factors in some cases. As with most forms of sexual activity, anal sex participants risk contracting sexually transmitted infections (STIs). Anal sex is considered a high-risk sexual practice because of the vulnerability of the anus and rectum. The anal and rectal tissue are delicate and do not provide lubrication like the vagina does, so they can easily tear and permit disease transmission, especially if a personal lubricant is not used. Anal sex without protection of a condom is considered the riskiest form of sexual activity, and therefore health authorities such as the World Health Organization (WHO) recommend safe sex practices for anal sex. Strong views are often expressed about anal sex. It is controversial in various cultures, especially with regard to religious prohibitions. This is commonly due to prohibitions against anal sex among males or teachings about the procreative purpose of sexual activity. It may be considered taboo or unnatural, and is a criminal offense in some countries, punishable by corporal or capital punishment. By contrast, anal sex may also be considered a natural and valid form of sexual activity as fulfilling as other desired sexual expressions, and can be an enhancing or primary element of a person's