Police are a group of people whose job is to enforce laws, help with emergencies, solve crimes and protect property. A person who carries out this duty is known as a police officer. They work out of a police station. Police are trained in first aid and rescue, because police officers are often one of the first people to get to a place where people are sick or injured, such as a car accident, or a fire.

Naming
A police agency may be called a police force, police department, police service, constabulary, civil guard or protective service. A gendarmerie is a police force that is part of the military, although its members rarely do actual military work.

Most police forces in the United States name themselves as "[Place] Police Department", such as New York City Police Department. State police forces are usually known as either "[State] Highway Patrol" or "[State] State Police". In the United Kingdom, most are "[Place] Police" or "[Place] Constabulary". In Canada and other English-speaking countries, "[Place] Police Service" is common. Ireland's police are called the Garda Síochána.

A law enforcement agency is any agency that enforces the law. In the United States, there are some law enforcement agencies that are not called police forces but carry out similar work, such as the Federal Bureau of Investigations. One common type is a sheriff's office (also sheriff's department), an agency that is led by a sheriff.

Those who carry out policing duties are known as police officers. They may also be known as policemen

Powers
The police have different powers to help them do their job. These powers are different in different countries. Most police officers have the power to arrest people, search people, and search houses/properties. They sometimes carry equipment such as guns, batons, tasers, or pepper spray. The area where police officers can use these powers is called their jurisdiction. If officers are outside of their jurisdiction, another police force with jurisdiction can then use their powers.

Duties
The police deal with:
 Preventing crime and protecting the public. They do this by patrolling on foot in uniform and in police cars. This can stop some forms of criminal behavior.
 Responding to crimes. When someone calls the police to say that a crime is happening, they must send some police officers to arrive at the scene very quickly. They will try to stop the crime and catch the person doing it.
 Investigating crime. This means that the police try to find out who did the crime.
 Arresting and detaining suspects. When the police believe that someone has committed a crime, the police arrest them, take them to the police station and ask them questions. However, it is the prosecutors and not the police who have the final say on whether a suspect gets charged.
 To help with emergencies or problems that are not crimes. This may be car accidents, fires, or people who are sick, hurt or lost. The police work with firefighters, ambulances, and rescuers. They might direct traffic, help lost children, or give traffic tickets.

Parts of police departments
Most police departments have officers in two main groups: a "patrol" group with officers who wear uniforms, and a "detective" group with officers who wear normal clothing. 

Patrol officers travel through their area. They may travel by foot, on bicycle or motorcycle, or in marked cars. The cars have warning lights and sirens that can be used. The sirens make a loud sound. Patrol officers enforce motor vehicle and criminal laws. In some locations patrol officers manage the local jail.
Detectives work on investigations that are more complex. They try to find fraud, illegal drugs, and sex crimes like prostitution, human trafficking, and rape. Prostitution is not a crime in all countries.

Not all countries use the same words to describe these groups. In the United Kingdom, for example, patrol officers form the "uniform branch", while detectives work within the CID ("Criminal Investigation Department"). Also in the United Kingdom, not all police officers are armed, these police officers form an "Armed Response Unit" which comes under other names in different constabularies, in the Metropolitan Police Service, it falls under SFC (Specialist Firearms Command) which all MET Armed Police fall under  

Police uniforms, equipment and methods vary depending on the country. In some places, groups of police train for special jobs such as dealing with riots or dealing with highly dangerous criminals.

Police in different countries
Different countries have different ways of organizing their police. Some countries like South Africa, Ireland and New Zealand have just one police force. Other countries have more than one. France has two police forces, one for cities and another for rural areas. Chile also has two, one for patrol and another for investigations.

Some countries have two or more levels of police forces. For example, most policing in Australia is carried out by the six state police forces, but there is also the Australian Federal Police who police the whole country. Germany has a similar system. The United Kingdom and Switzerland have many local police forces and several national agencies, but no actual national police force. In Canada, local governments can choose to either run their own police force or give the job to a bigger one. So most Canadian cities have their own police, while most rural areas are policed by the Royal Canadian Mounted Police, which is also the national police.

The United States has over 17,000 law enforcement agencies. Many areas have four levels of law enforcement agencies. For example, Los Angeles has the Los Angeles Police Department but there are many other agencies that can work in the city. This includes the county-level Los Angeles Sheriff's Department, the state-level California Highway Patrol and over 100 federal (or national) law enforcement agencies.

Worldwide, police are a small percentage of the number of people they serve. On average there are 303.3 police officers per 100,000 people.

Equipment
In most countries, police officers carry guns during their normal duties. In the United Kingdom, New Zealand, Ireland and a few other countries, most police officers do not carry guns. Officers may also carry pepper spray, electric shock weapons (such as tasers), and batons for defense. Police officers also wear handcuffs to detain suspects.

Officers communicate using radio devices. The radios can be on both the uniform and in the patrol vehicle.

Related pages
Police officer
SWAT team

References

Other websites
1860-1870 picture of  San Fransico Police man
Police History book  
Police Pictures links

Law
Emergency services