The London Oyster Card is a smart card used for travel on public transport in London. It can be used on the Tube, buses, trains, and even some river services. The card allows users to pay for their journeys quickly and conveniently, offering lower fares compared to cash payments. To obtain an Oyster Card, travelers can order one online or purchase it at various locations, including Tube stations. Users can top up the card with credit as needed. The Oyster Card is a popular choice for both residents and visitors, making travel around the city more efficient.