Oral - with direct reference to Oral Sex, it's a sexual practice where the genital organs of a person are stimulated with the mouth by another person.
Oral sex can be done by anyone regardless their sexual orientation.
Some forms of oral sex are: Cunnilingus oral stimulation on a female; Fellatio when performed to a male. When a person Anus is stimulated orally it's also a form of oral sex called, Anilingus.
In live adult entertainment you can watch an oral sex show especially in Couples and Lesbians categories, while solo Models can simulate an oral sex with a dildo and the male customer can imagine that the dildo is his penis.