Oyster card
What it really means
A blue plastic smartcard for paying on London transport. You load money onto it and tap it on the yellow readers. A contactless bank card now does the same job for most people.
Context, tips & common mistakes
Oyster is London's transport smartcard: buy one at any Tube station machine or corner-shop newsagent displaying the sign, load pay-as-you-go credit, and tap exactly as with contactless — same fares, same daily caps. In the phone era it earns its keep in specific cases: visitors whose foreign bank cards charge per-transaction FX fees, children and students (discount photocards only exist as Oyster), railcard holders (the discount links to Oyster at a station, giving a third off off-peak fares), and anyone whose phone battery is a liability.
Register the card online: registration protects the balance if lost, shows journey history, and lets you claim incomplete-journey refunds. Unspent credit and the card fee have refund routes via machines and the TfL app. One per person — card-sharing fails at inspection, since the card, not the human, holds the ticket.