I guess I didn’t explain it clearly enough, tbf it’s a weird concept to get your head around though. Here are some Wikipedia articles that might help you understand what I’m trying to say:

https://en.m.wikipedia.org/wiki/Government_of_New_York_City

https://en.m.wikipedia.org/wiki/Boroughs_of_New_York_City

>All five boroughs came into existence with the creation of modern New York City in 1898, when New York County (including The Bronx), Kings County, part of Queens County, and Richmond County were consolidated within one municipal government under a new city charter. All former municipalities within the newly consolidated city were eliminated.

>New York City was originally confined to Manhattan Island and the smaller surrounding islands that formed New York County. As the city grew northward, it began annexing areas on the mainland, absorbing territory from Westchester County into New York County in 1874 (West Bronx) and 1895 (East Bronx). During the 1898 consolidation, this territory was organized as the Borough of the Bronx, though still part of New York County. In 1914, Bronx County was split off from New York County so that each borough was then coterminous with a county.

>When the western part of Queens County was consolidated with New York City in 1898, that area became the Borough of Queens. In 1899, the remaining eastern section of Queens County was split off to form Nassau County on Long Island, thereafter making the borough and county of Queens coextensive with each other.