Short answers, pulled from the story.
The police are a constituted body of people empowered by a state to enforce the law and protect public order and the public itself. Their lawful powers include arrest and the use of force, legitimized by the state's monopoly on violence. They are usually public sector services funded through taxes.
The word police was first attested in English in the early 15th century, originally meaning public policy, state, and public order. It comes from the Middle French police, in turn from the Latin politia, a romanization of the Ancient Greek politeia meaning citizenship and civil polity, which derives from polis, the Greek word for city.
The first statutory police force was probably the High Constables of Edinburgh, formed in 1611 to police the streets of Edinburgh. The first centrally organized and uniformed police force was created by King Louis XIV in 1667 to police Paris, headed by a lieutenant général de police first held by Gabriel Nicolas de la Reynie.
Uniformed police make up the majority of a police service and mainly respond to calls for service and conduct patrols to prevent crime. Detectives handle investigations, typically make up roughly 15 to 25 percent of personnel, and usually wear business attire rather than uniforms, sometimes working undercover.
Some countries such as Austria, Chile, Israel, New Zealand, the Philippines, South Africa, and Sweden have a single national police force. France pairs a civilian Police Nationale with a paramilitary National Gendarmerie, while the United States runs a decentralized system with over 17,000 state and local law enforcement agencies.
Ancient China used prefects, who could include women, dating to the Spring and Autumn period. Ancient Egypt had warriors with wooden sticks and an elite desert force called the Medjay, ancient Athens used about 300 Scythian Archers, and Rome relied on the army along with squads of vigiles who served as night watchmen and firemen.