Is Citi Bike free in NYC?

Excuse me, I'm a bit confused about the pricing structure of Citi Bike in New York City. Could you please clarify whether the service is offered for free or if there are any associated costs for riders? Additionally, if there are fees, could you provide an overview of the different pricing options and any potential discounts or promotions that might be available? Thank you for your assistance in helping me understand the financial aspect of utilizing Citi Bike in NYC.