The London Travelcard is paper ticket that is valid for unlimited travel on 7 consecutive days. It can be used on all forms of transit, including the London Underground (the Tube), London Overground, bus, tram, DLR, and the National Rail services.
The Travelcard is a good option for travelers who expect to use London transit every day for a week. The card is valid for 7 days after its first use, until 4:30AM on the day after the expiry date. If you need more days, single-day Travelcards or Oyster Cards can be purchased from Visitor Shops or Tube stations.