Cyberbullying is a type of bullying, which in turn is a type of aggression. This paper gives a brief history of research, and discusses definitional issues around cyberbullying, and three challenges facing researchers; it then reviews some basic findings about prevalence, age and gender differences, predictors of involvement, and effects and correlates of involvement. It concludes with evidence as to whether cyberbullying is getting worse, on coping strategies, and on resources, guidance and intervention.