The New York City subway system is one of the largest in the world, this includes the largest number of stations, the most ridership in the Western world, and simply in terms of recognition. It's extremely recognizable, and despite the reputation for smells and crime, actually amazingly effective and service oriented.
The subway is served by its own police force, can be tracked online and is remarkably efficient. With connecting service to the airports and serving all of Manhattan, there is no wonder that it has become a tourist attraction on its own. Additionally, there is an array of artwork throughout the system for people to enjoy.
To get more information about the system, complete with service status, you can get the information on the official MTA website.
Enjoy your time in the city and hopefully this information will help you get around.