Anger is an emotion, while aggression is a behavior. They differ entirely in one central dimension - control.

• You can't control your emotions directly. In the legal system, nobody gets sent to prison for how they felt, regardless of how angry they were. They get punished for what they do.
• You can influence your emotions indirectly by how you think and behave. For example, when you focus on how terrible all the drivers in your town are, your anger will likely increase. But, if you listen to music and think about how grateful you are, your anger will probably subside.