Children who meet criteria for a behavioural disorder such as conduct disorder or oppositional defiant disorder have a pattern of behaviours characterised as aggressive or antisocial.
Most children misbehave, or are aggressive, defiant or have tantrums from time to time. That’s perfectly normal. To reach a diagnosis of conduct disorder or oppositional defiant disorder, the behaviours have to be more frequent and/or more severe than their same aged peers. But it is important to remember that many children who meet diagnosis of a conduct disorder or oppositional defiant disorder are not necessarily doing different kinds of things compared to their same aged peers, it is just that they stand out for how much or how intensely they do them.