It is rather difficult to come up with a common definition of “borough” as it means different things to different peoples. In New Jersey, it means a self-governing incorporated town, while in Alaska it is a civil division of the state, much like a county in most other states. In New York City, a borough is one of its five administrative divisions. The five are Manhattan, Brooklyn, Staten Island, the Bronx, and Queens.
Modern New York City was formed in 1898 when Manhattan and the Bronx (which were cities within New York county at the time) were consolidated with the independent city of Brooklyn along with several municipalities in Kings County. Adjacent areas were incorporated as well. Areas in the western portion of Queens County became Queens Borough, while the whole of Richmond County was included in the consolidation as Staten Island Borough. Eventually, the Bronx County would be carved out of the County of New York. The area of Queens County left over from the formation of Queens Borough, would later be established as Nassau County. Owing to these developments, the five boroughs of New York City are now coextensive with their counties, as follows: New York County, Manhattan, Brooklyn, Queens County, Queens, Bronx County, Bronx, Staten Island, Richmond County, and Kings County.
When these boroughs were formed, all county, city, and town governments within the geographical area were dissolved. Governance was centralized in a government headed by a mayor as the executive and a unicameral legislative council consisting of 51 members.
The boroughs, for their part, are represented by a borough president but there is no legislative body. They have their own borough hall, except that Manhattan does not call it a borough hall but the Manhattan Municipal Building.
The president, however, has minimal executive powers. Indeed, many observers see the office as largely ceremonial. However, they do have the opportunity to provide advice to the Mayor on matters relating to their respective boroughs particularly on land use and their budgets. They have a small discretionary fund for borough projects, and they can create and chair Community Boards.
Since the New York City boroughs are also counties, they elect their own district attorney. They also get to elect judges, but once elected, the judges can serve anywhere within the city.