I have just purchased a rail ticket for London Kings Cross, but the ticket says to "London Terminals" Does this mean I can use it on the tube, or do I have to purchase another ticket? I am not familiar with London. Many thanks in advance.
London Terminals just means mainline stations that the trains from your area go into - ie Euston or Kings Cross or Waterloo etc. It will not include the tube unless you specifically asked for it to and paid accordingly.
Depending on the type of ticket and where you are travelling from it MAY be valid on a different train route to St Pancras, Liverpool Street, maybe Euston instead of Kings Cross.