The Perineum is the general region or the spot between the vagina opening and the anus.

The Perineum and The Female Sexual Pleasure
The perineum is an erogenous zone and plays an important role in female sexual arousal.
It is rich in sensitive nerve fibers and is extremely and pleasurably sensitive to erotic touch and stimulation.
When a girl (or a woman) becomes sexually aroused via foreplay, the blood vessels and erectile tissue beneath the skin of the perineum fill with blood, making it intensely sensitive to erotic touch and stimulation during cunnilingus (oral sex).
Particularly, a warm wet tongue on the perineum feels incredibly pleasurable to women and have them dripping wet in no time.
The Perineal Sponge – PS-Spot
Rubbing of the perineum stimulates the PS-Spot… and adds to the pleasure and arousal of a woman (or girl).
And there you have it…
…the perineum.