A government is an organization in a community or political entity that has the power to enact and enforce laws and maintain the peace and order. A government is necessary since is it considered the leadership of an organization, community or political entity.
Laws are important since it defines the behavior of citizens. It defines which are legal or illegal. Without laws, an activity can not be known if it a crime or not. The law-making role of the government creates a code of conduct for individuals to follow.
Another role of the government is the maintenance of peace and order. The police and fire department ensures that crimes like murder, theft, arson, etc. are prevented or minimized. If a crime does happen, it is their role to look into how the crime happened and apprehend the perpetrators.
Government also promotes harmony though justice and equality. Once a crime is solved by the police, it is the duty of the judicial branch of the government to bring the perpetrator to court for fair trial and punishment. It makes sure that the right person gets into jail for the right reason.