Bullying is a distinctive pattern of deliberately harming and humiliating others. It's a very durable behavioral style, largely because bullies get what they want—at least at first. Bullies are made, not born, and it happens at an early age, if the normal aggression of 2-year-olds isn't handled well.
Bullies couldn't exist without victims, and they don't pick on just anyone; those singled out lack assertiveness and radiate fear long before they ever encounter a bully. No one likes a bully, but no one likes a victim either. Grown-up bullies wreak havoc in their relationships and in the workplace.
Children grow up without the kinds of experiences that lead to the development of social skills, and free play is on the decline. It's in playing with peers, without adult monitoring, that children develop the skills that make them well-liked by age-mates and learn how to solve social problems.