Manhattan is where most of the major landmarks, historical districts and shopping areas are in NYC. Each of the Boroughs has an interesting history and great places to visit, but Manhattan has all the glamorous well known neighborhoods and street names.
Manhattan is a long thin island joined to each of the other boroughs by bridges, train tunnels and ferries. The Eastern side of Manhattan has the East River running along it and the Western side of Manhattan has the Hudson River running along it
Manhattan’s numbered roads are all called either East or West STREETS. The division between East and West is along Fifth ave. (The East/West division between streets are aligned with the Hudson river rather than a compass bearing, so the East/West designation is not strictly accurate). Because the East/West STREETS run across the island they are, relatively speaking, short.
The roads running North and South are all called AVENUES. To get a sense of direction in Manhattan, if you are on a train going towards The Bronx you are going North, if you are on a train heading towards Brooklyn you are going South. (Directions in the subway always include reference to either the Bronx or Brooklyn, boroughs which Manhaattan connects to). Because Manhattan is 14 miles long, the AVENUES are all, relatively speaking, very long.
Excepting the lower part of Manhattan which is a special case (see sheet on History of Manhattan’s layout) New Yorkers navigate by referring to an address on either a StREET or an AVENUE, and then they will say, if it is a STREET address ‘between such and such Avenue’. If it is an address on an AVENUE they will say ‘between West 25th St and West 26th St’ or between East 25th and East 26th Street’ as the case may be. This allows you to locate the address very accurately on the Manhattan grid. The Avenues especially are very long and being able to locate the grid reference for an address saves a great deal of time.
The special case is the road called Broadway. It follows an historical route, rather than being a part of the grid and runs South/North from the lower part of Manhattan right up to just below Central park, and unlike other long North/South streets it doglegs as it goes. (Again see the sheet on the History of Manhattan’s Layout). So if you are given an address on Broadway it is crucial you get grid reference otherwise it’s a very long walk.
The final point is that the lower part of Manhattan was where European settlement first took place and the streets are not laid out in a grid. They are all higgeldy-piggeldy and not hard to navigate if you have a good map, but they lack the brisk numerical certainty of the area North of East Houston St in the East village which is where the grid pattern starts.