"The transaction is authorized either online and offline. For an online authorization, transactions proceed as they do today in the U.S. with magnetic stripe cards. The transaction information is sent to the issuer, along with a transaction-specific cryptogram, and the issuer either authorizes or declines the transaction. In an offline EMV transaction, the card and terminal communicate and use issuer-defined risk parameters that are set in the card to determine whether the transaction can be authorized. Offline transactions are used when terminals do not have online connectivity (e.g., at a ticket kiosk) or in countries where telecommunications costs are high."

http://www.emv-connection.com/emv-faq/

It's in wide use in Europe, for instance a ticket machine on a train or tram, or for low-value transactions (bus tickets, fast food), or where there's no connection (purchase on a plane -- where they will probably only accept credit cards beyond a certain amount).