The MetroCard is a smart card used for fare payment on public transportation in New York City. It can be used on the subway and buses, allowing riders to easily access the city's extensive transit system. The card can be purchased at vending machines and subway stations, and it can be loaded with a specific amount of money or unlimited rides for a set period. Riders can refill their MetroCard balance at various locations, including convenience stores and subway stations. The card offers discounts for multiple rides and is a convenient way to navigate the bustling city without needing cash for each trip.