Transit cards are electronic cards used for paying fares on public transportation systems, such as buses, trains, and subways. They can be loaded with money or specific travel passes, allowing users to tap the card at designated readers for quick access to transit services. This system helps streamline the boarding process and reduces the need for cash transactions. Many cities offer transit cards, including New York City's MetroCard and San Francisco's Clipper Card. These cards often provide discounts for frequent travelers and can be recharged at kiosks or online. They promote efficient and convenient travel within urban areas.