Sex
Sexual Intercourse is for humans: The Male will insert his penis into the Female's vagina or anus. The feeling of the penis in the Female's vagina or anus, touching the walls, sexually stimulates the Female. If she is sexually stimulated enough, she will have what's called an "Orgasm", in which she releases a sugary liquid from her vagina. The feeling of the vagina or anus around the penis, and mainly on the bottom, and around the bottom of the head(the foreskin), sexually stimulates the Male. The Male's penis has two tubes: one for urinating and one for ejaculating. When the Male is sexually stimulated enough, the bottom tube(the ejaculant tube) will shift with the top tube. This is known when the Male can't control his penis. Then, and only then, will the massaging feeling of continuous thrust "tickle" the Male, as he's having a male orgasm, and ejaculating both sperm and semen. The semen gives the sperm energy. The sperm must fertilize the eggs in the Female.
Teacher: "Okay class, today I'm gonna teach you about Sex."
Students: "Okay."