Oral sex is a sexual activity in which two partners stimulate each others genitals in a sexual way. To perform oral sex (fellatio) on a man, the mouth is placed around the penile shaft and used to arouse the man by licking, sucking, and/or kissing his penis and testicles. To perform oral sex (cunnilingus) on a woman, the partner's mouth is used to lick, suck, and/or kiss the vulva, vagina and clitoris. Oral sex can occur between a man and a woman, two men, two women, or multiple partners, and carries an increased risk of STDs. Slang terms include: Blow job, giving head, going down, eating out and more.