However, if this field is not meaningful, that is it is strictly for the database to internally identify a unique record, it is a surrogate key or blind key. In this case Person ID probably is an AutoNumber field, and it should not be used except internally by the database.
It's the city of New York that is divided into boroughs. In 1898, the modern city of New York was formed by merging the County of New York (modern day Manhattan and the Bronx), the then independent city of Brooklyn, Richmond County, and the western parts of then Queens County (the remainder is modern day Nassau County). To make people happy, the new city was divided into boroughs (similar to London). The original city of New York became Manhattan (named after the island it is on). The remainder of New York County became The Bronx. Brooklyn stayed Brooklyn. Queens County is also Queens. And Richmond County became Staten Island (also named after the island it is on).
In reference to New York City, a borough refers to a semi-autonomous government unit within the city. Prior to 1898, New York City basically referred only to what is now called Manhattan. Brooklyn was a separate city, Queens was a county composed of smaller villages, etc.