The verb fulfill means to fill a need or want. To fulfill yourself personally means to follow your inner passion, like flute-playing, no matter who thinks it's silly.
Fulfill can also mean to meet expectations, or live up to a standard. If you fulfill your teacher's requirement of good behavior and good test scores, she'll give you a star. Finally, fulfill can mean to put into effect, or carry out. You'll fulfill the cookie orders when you deliver boxes of those tasty treats to the people who bought them.