Consider two children in the same classroom, one introverted and one shy. The teacher is organizing an activity for all the children in the room. The introverted child wants to remain at her desk and read a book because she finds being with all the other children stressful. The shy child wants to join the other children, but remains at her desk because she is afraid to join them.
Children can be helped to overcome their shyness, but introversion is as much a part of a person as is hair or eye color. In other words, people can get therapy for shyness, but not for introversion. Not all introverts are shy. In fact, some have excellent social skills. However, after engaging in social activities, an introvert will be emotionally drained and need time alone to "recharge" their emotional batteries.
While therapy can help the shy person, trying to turn an introvert into an outgoing extrovert can cause stress and lead to problems with self-esteem. Introverts can learn coping strategies to help them deal with social situation, but they will always be introverts.
If you think your child might be an introvert, you might want to look at some of the traits of introversion and see how many of them your child has.