Clitoral Complex 101
First, a definition. The clitoral complex is not only the external clitoris, but also internal erectile tissues and nerve endings that reach from the external clitoris to the front, distal (farther end) of the vagina. These sensitive erectile tissues in fact have wings (called bulbs) that are attached to the external clitoris but then hug the vaginal opening.
The clitoris and its wings are responsible for most orgasms (with the input of the brain of course). The clitoral complex, like all things in the human body, varies from woman to woman. So that some women have great sensitivity on the front side of their vagina (aka G spot), as palpitation there can hit the clitoral complex or the nerve endings attached to it, giving similar responses to external clitoral stimulation, which most women would agree is a good thing. External clitoral size can also vary widely from 0.3 cm in width to over 3 cm, and when aroused this external glans will usually swell in size to assist with arousal, a nice feature. The internal bulbs also swell, which help shut off the urethra by pinching it, so that even moms of 4 or 5 kids don't pee during sex for the most part. Although a full bladder and the resulting pressures can result in leakage even from childless women.
In a study published last year by Dr. Herbenick, at the University of Indiana, thousands of women 18-94 were surveyed and only 18.4% of them reported having orgasm from vaginal penetration alone. The rest surveyed reported a desire for clitoral stimulation to either achieve an orgasm at all or a "good" one, either by itself (such as cunnilingus) or in addition to vaginal penetration by penis or sex toy.
Understanding your clitoris and it's complex complex can help you know where and how to start feeling out what is the best way to achieve orgasm for your body. And know that rubbing your clitoris or asking your partner to do so with fingers or vibrator while having vaginal sex can be the key to coming for most women. Simultaneous orgasms by both partners with vaginal sex alone, as shown in most movies, is as real as all the physics in movies. I'm sorry, cars don't blow up in fire balls that blast them 50 feet high.