A piece of flesh which protects and covers the clitoris. During arousal, the clitoris emerges from the clit hood and becomes engorged with blood, heightening sensitivity. The function is similar to the male foreskin, which protects the sensitive head of the penis. Again, during arousal, the penis head emerges and becomes engorged. Circumcision is reported to lead to a loss of sexual sensitivity (the nerve endings of the penis head become toughened, and feel less sensation), and can explain some male attitudes towards sex. Male circumcision is similar to the barbaric practice of female circumcision or genital mutilation. I expect the female version is probably a little bit more painful, though. (as it often entails the removal of much more than the clit-hood, and the use of non-surgical instruments)