The clitoris (pronounced: KLIHT uh rihs) is a sexual organ in the body of female mammals, located near where the labia minora meet anteriorly. The visible knob-like portion is located above the opening of the vagina. Its function is inducing sexual pleasure and orgasms.
It is formed out of corpora cavernosa and embryologically arises from the same tissue that forms the male penis. The clitoris has a 'hood' of tissue that is embryologically comes from same tissue that becomes the foreskin in males. The trigger for forming a clitoris instead of a penis is the action of testosterone (see why do women have a clitoris?) in early in utero.
Cliterectomy is a barbaric practice still carried out today in some societies as part of female circumcision.