EMV fallback transaction is an important concept, allowing companies, which accept card payments, to make the process of handling of EMV cards more flexible. EMV standard was introduced to make card payments more secure. However, in some cases EMV card chip cannot be read by the payment terminal. For instance, either the chip itself or the EMV card reader may be damaged in some way.
When the chip cannot be scanned, the transaction cannot be processed as an ordinary EMV transaction and the so-called fallback transaction has to be attempted. The two main types of EMV transaction fallback are swiped fallback and manual fallback. If the terminal cannot read the chip, first the swiped fallback is attempted, i.e. the EMV card is swiped like a magnetic stripe card. If swiped fallback fails, the card number can be input into the terminal manually.
If the payment terminal is capable of accepting EMV contact and EMV contactless payments, both these payment types can be attempted. If they both fail, swiped and manual transaction fallback can be attempted afterwards.
Read more on EMV transaction fallbacks in the respective article on Paylosophy.