EMV is a set of specifications for interoperation of smart cards ("Chip cards") and smart card capable points of service (POS) and ATMs (Automatic Teller Machine) for authenticating credit and debit card payments.
The EMV standard defines the interaction at the physical, electrical, data and application levels between smart cards and smart card processing devices (mainly a POS or an ATM with a smart card reader) for financial transactions. Portions of the standard are heavily based on the smart card interface defined in ISO 7816.
Values involved in an EMV transaction are transported and identified by a tag which defines the meaning of the value, the format and the length.
Working on EVM capable smart cards and acceptance devices one of the most complex issue is to understand the meaning of the tags involved in a transaction. I collected in this page all EMV tags with a detailed description.