The terms Introvert and Extrovert (originally spelled Extravert by Carl Jung, who invented the terms) are referred to as "attitudes" and show how a person orients and receives their energy. In the Extraverted attitude the energy flow is outward, and the preferred focus is on people and things, whereas in the Introverted attitude the energy flow is inward, and the preferred focus is on thoughts and ideas.
Even as an adult, my vision of an extrovert was an in-your-face salesperson who only wanted to build a shallow relationship with you so they could sell you something.
Expecting an introvert to learn to become an extrovert is akin to expecting a left handed person to become right handed, just because the majority of the population is right handed.
Extroverts recharge themselves by going to a party, and an introvert recharges themself by doing quiet activities, to let their brains rest.
An extrovert may envision a large project, but balk at tackling the small details that are the realm of the introvert.
Extroverts are often frustrated by the introverts aversion to socializing.
Its important for extroverts to remember that introverts can become numbed when they encounter too much energy at once and that they tend to be day-dreamers who get lost in their own thoughts.