The Crown Prosecution Service (CPS) helps make sure that people follow the laws in England and Wales. They're a bit like the teacher at school who makes sure everyone behaves and follows the rules.
The CPS works with the police and other people in the criminal justice system to decide if someone should go to court for breaking the law. They decide if they have enough evidence to prove that someone has really done something illegal.
If they think there's enough evidence, they will take the person to court and argue their case. This is like when you argue with your friend about who had the toy first, but it's much more serious and grown-up.
The CPS also helps victims of crimes by supporting them in court and making sure that they get justice. They take their job very seriously and want to make sure that everyone is treated fairly and that the right people are held responsible for their actions.
So, basically, the CPS is like a very important grown-up who makes sure that everyone follows the rules and that people who break them are held accountable for their actions.