The New York City MetroCard is a smart card used for fare payment on the New York City Subway and MTA buses. It can be purchased at vending machines, subway stations, and authorized retailers. Riders can load the card with a specific amount of money or opt for unlimited ride options for a set period. MetroCards come in two main types: pay-per-ride and unlimited. The pay-per-ride card deducts a fare each time it is used, while the unlimited card allows for unlimited rides within a specified time frame. The card is a convenient way to navigate the city's extensive public transportation system.