During sexual intercourse, a man places his penis inside a woman's vagina and moves it backwards and forwards. The woman may also move her hips back and forth, or in a circular motion. The friction caused by this movement, together with the warmth and pressure of the vagina, causes the man to have pleasurable feelings in his penis. As intercourse continues, these feelings grow stronger and stronger until the man has an orgasm and ejaculates, at which time semen then shoots out from the end of his penis into the woman's vagina. The semen can make the woman pregnant.