Answer:
The police force was designed with the motto "to protect and serve". they uphold the law, and they make sure the streets are safe for citizens. this includes performing investigations and making arrests. The Police Force's job is too extensive to explain on a damn internet question, but they mostly make sure we stay safe, the laws are followed, people aren't acting crazy, and, MOST IMPORTANTLY, they make sure the streets are safe from terrible things like....marijuana.