VERY good question. Moderators are staff members of the Club Penguin Team. They have the ability to edit Club Penguin's interface and settings. They can also ban a penguin if they break the rules and guidelines. Agents can be penguins like you and me. You have to click the "M" badge on the right top corner of the screen and pass the quiz to become an agent. Agents do missions and report penguins for breaking the rules. If you aren't an agent, you can still report, but you can't do missions.