You can put a credit on the Oyster Card. With this credit you can use Public Transport in London. The Oyster Card automatically calculates the cheapest rate, so you do not have to worry about that. The day-capping applies to zones 1 to 6. This means that you will never have to pay more than a certain maximum amount per day for traveling with public transport in those zones.
With the Travelcard you can choose to travel by public transport for 1 or 7 consecutive days in the zones in which you want to travel. It seems that traveling with a Travelcard is gradually being discouraged. Traveling with a 1-day Travelcard is (in 2018) always more expensive than day-capping. A 7-day Travelcard can be cheaper if you travel a lot with public transport. Please check this webite for an overview.
With the Travelcard you can:
The Travelcard is not valid for these train lines:
When you go through a zone that is not valid on your Travelcard, this is automatically paid from the credit you have on the Oyster Card.
A 1-day Travelcard is always a paper version. A 7-day Travelcard can be put on your Oyster Card, but you can also buy a paper version. With the Travelcard you can travel 1 day or 7 consecutive days. You can choose how many zones you want to travel in.
A passport photo is required for a paper version of the Travelcard. When you buy a paper Travelcard at a National Rail station in London, there is a special offer. You can visit attractions (such as London Eye, Tower, Shard etc.) with 2 people for the price 1 person. See here for more details and conditions. You must order tickets for the atractions in advance.
The Oyster Card can be used for bus, metro, tram, DLR, London Overground, TfL Rail, Emirates Air Line, River Bus services and most National Rail services in London (zone 1-9). Click here for an overview. In addition, it is valid for the train connection to Gatwick airport (Gatwick Express, Thameslink and Southern services), but not valid on the Heathrow Express and Heathrow Connect services between Hayes & Harlington and Heathrow.
The Visitor Oyster Card must be sent in advance because it is not available in London. Shipping costs are therefore included. You can, for example, purchase these tickets from the British Tourist Board. You can also buy a Visitor Oyster Card at TfL (Transport for London). The shipping costs for shipping without track and trace are £3.25, and costs £9.75 per express.
You get a discount at a number of restaurants, museums and shops with the Visitor Oyster Card. A complete list can be found here. With a regular Oyster Card you pay £5,- deposit, which can be refunded later. With a Visitor Oyster Card you pay 'activation costs', these will not be refunded.
The "regular" Oyster Card can be bought at many locations in London, such as all tube and railway stations.
Check this site for more information about the Visitor Oyster Card.
Up to and including the age of 10, children can generally travel with adults free of charge. From the age of 11 it becomes slightly more complicated.
Children up to and including 4 years of age travel for free with an adult.
Children from 5 to 10 years old travel free with paying adults (up to 4 children per adult). This applies to journeys by metro, DLR Overgroud, TfL Rail and a very limited number of National Rail lines. This is a bit confusing because adults who use the Oyster Card can use most trains from the national rail. Check this website for more information and an overview of the train lines.
If you want to travel for free with most other National Rail lines, a 5-10 Zip Oyster Photocard is required. In addition, a 5-10 Zip Oyster Photocard offers the advantage that children can travel at a child rate at Southeastern high speed services between St Pancras International and Stratford International, Gatwick Express Southern and Thameslink services between Coulsdon South and Gatwick Airport.
The Zip Oyster Photocard for children must be ordered online and can then be picked up at a Visitor Center. The confirmation email and the passport/id must also be shown for checking the age of the child. There must be at least a 28-day period between the time you order the Zip Oyster Photocard and the day you pick up the card at the Visitor Center. Look at this website for more information. The costs are £10,-. Look here for the locations/opening hours of the Visitor Centers.
The category of children aged 11 to 15 years are no longer allowed to travel with adults for free. There is a number of possibilities:
The credit on the Oyster Card does not expire, so you can keep the Oyster Card for a next visit or give it to others who will visit London. Only the deposit from an ordinary Oyster Card can be re-claimed, not from a Visitor Oyster Card! If the credit is less than £10, then the credit and deposit (if applicable) can be re-claimed at a subway ticket machine. This only applies if at least 48 hours have elapsed since the first use of the card. If the credit is more than £10,-, the possibilities are somewhat more limited. You can then go to a Visitor center (not in Gatwick) or call. Click here for a regular Visitor Card and here for a Visitor Oyster Card.