The 오이스터 카드 is a smart card used for public transportation in 런던. It allows users to travel on the 지하철, 버스, and other forms of transport easily and efficiently. The card can be loaded with credit, which is deducted automatically when you tap in and out at stations. To obtain an 오이스터 카드, you can purchase one at ticket machines, online, or at various retail locations. It offers discounted fares compared to single tickets, making it a cost-effective option for both residents and tourists exploring the city.