The Oyster Card is a smart card used for electronic payment on public transport in London. It allows users to travel on the London Underground, buses, and other services, offering a convenient and cost-effective way to pay for fares. Users can load money onto the card and tap it on card readers at stations and bus stops. Introduced in 2003, the Oyster Card has become a popular choice for both residents and visitors. It provides discounted fares compared to cash payments and can be topped up at various locations, including ticket machines and online.