The Clipper Card is a smart card used for electronic fare payment on public transportation in the San Francisco Bay Area. It allows users to load funds or transit passes and can be used on various transit systems, including BART, Muni, AC Transit, and Caltrain. The card simplifies the payment process, making it easier for commuters and travelers to access multiple transit services with a single card. Users can purchase a Clipper Card online, at ticket vending machines, or at select retail locations. The card can be reloaded with cash or credit, and users can also manage their accounts online to check balances and transaction history.