So you know how we have rules and laws in our everyday life that we have to follow? Well, the Vatican City is like its own country and they also have their own rules and laws. When someone breaks these rules, that's called a crime.
Now, the Vatican City is a really small place and lots of people who live there are members of the church or work there. They try really hard to keep the place nice and safe. But sometimes, just like in other countries, people still break the rules and commit crimes.
The Vatican City has its own police force called the Swiss Guard. They work hard to make sure everyone follows the rules and is safe. They investigate crimes and arrest people who break the law.
Sometimes, crimes can be very serious like theft or assault. Other times, crimes can be smaller like littering or jaywalking. No matter what the crime is, it's important to follow the rules and respect the laws of the Vatican City.