Types of anal sex can also be a part of lesbian sexual practices. 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. Although anal sex most commonly means penile–anal penetration, sources sometimes use anal intercourse to exclusively denote penile–anal penetration, and anal sex to denote any form of anal sexual activity, especially between pairings as opposed to anal masturbation. Other forms of anal sex include fingering, the use of sex toys for anal penetration, oral sex performed on the anus ( anilingus), and pegging. 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.