There are two classes of taxis in NYC. Metered yellow (aka, Medallion) cabs licensed to respond to street hails anywhere in the city. And less regulated cabs, not allowed to respond to street hails. These operate in various neighborhoods and are ordered by phone dispatch. They may be called car services or limos depending on the market they serve.

That's how it's supposed to work, but the reality is that various areas are drastically underserved by yellow cabs, and the less regulated Gypsies operate there, and to an extent elsewhere, illegally responding to street hails. Hensel the name, which isn't intended as a complement.