Some townships and cities have municipalities that use different address systems for USPS. My parents live in a city called Mount Holly, but also a smaller township called Eastampton. So while they live in Mount Holly, their mail is addressed to Eastampton. You just need a little more understanding of government is all.

Hey, from Brooklyn here. Your friend isn’t correct at all.

Manhattan hasn’t been the sole borough of NYC since the late 1800’s. The Bronx was annexed in 1870s, and Staten Island, Queens, and Brooklyn were consolidated into NYC in 1898. At the time, the City of Brooklyn was considered to be as thriving of a city as the City of New York and many people weren’t happy with the consolidation, calling it “The Great Mistake of ‘98”. But since then, New York City is comprised of 5 boroughs: Staten Island, Manhattan, Brooklyn, Queens, and the Bronx.