Though introverts are a bit reserved kind of people, it would be wrong to associate their behavior with shyness. Such misconceptions about introvert personality create a wrong image about them, as a result of which they are often considered inferior to extroverts.
In psychology, introversion is defined as "the state of, or tendency towards being wholly or predominantly concerned with and interest in one's own mental life." An introvert is defined as "a person who tends to shrink from social contacts to become preoccupied with his own thoughts." It means he focuses primarily on his own mind, feelings, and affairs.
Unlike people with avoidant personality disorder, introverts don't suffer from anxiety attacks when it becomes necessary to maintain social contacts. However, some psychologists do suggest that being introvert to an extent wherein it interferes with your day-to-day activities can be referred to as a personality disorder.
An individual is less likely to display all the personality traits discussed here. It is not surprising to find several points of difference between two introverts. Similarly, an individual might display the traits of introversion in a lesser degree when around family members than what he would when with friends.
In the end, one needs to understand that almost all of us have the traits of both personality types―extroversion and introversion―with either type being more dominant than the other.