These cards are similar to magnetic stripe cards in terms of the data they share across the contactless interface. They are only distributed in the U.S. Payment occurs in a similar fashion to mag-stripe, without a PIN and often in off-line mode (depending on parameters of the terminal).
The security level of such a transaction is better than a mag-stripe card, as the chip cryptographically generates a code that can be verified by the card issuer’s systems.
Con-tactless EMV cards
These have two interfaces (contact and contactless) and work as a normal EMV card via their contact interface.
The contactless interface provides similar data to a contact EMV transaction, but usually a subset of the capabilities (e.g. usually issuers will not allow balances to be increased via the contactless interface, instead of requiring the card to be inserted into a device which uses the contact interface).
EMV cards may carry an “offline balance” stored in their chip, similar to the electronic wallet or “purse” that users of transit smart cards are used to.