Have you ever seen a police officer wearing a uniform? They are there to help keep everyone safe and follow the rules. Sometimes, when someone breaks a really big rule, the police officer can arrest them. This means they take the person to a special place called a jail.
The police officer has to have a good reason to arrest someone. They can only do it if the person is doing something illegal or dangerous, or if they have proof that the person has already done something really bad in the past.
When the police officer arrests someone, they have to tell them why they are being arrested and read them their rights. These are things the person is allowed to do like talk to a lawyer or ask for help if they need it.
After the person is taken to jail, they can have a trial to decide if they really did break the rules and what should happen to them next.