A payment processor is a system that enables financial transactions, commonly employed by a merchant, to handle transactions with customers from various channels such as credit cards and debit cards or bank accounts. They are usually broken down into two types: front-end and back-end.
Front-end processors have connections to various card associations and supply authorization and settlement services to the merchant banks' merchants. Back-end processors accept settlements from front-end processors and, via the Federal Reserve Bank for example, move the money from the issuing bank to the merchant bank.
In an operation that will usually take a few seconds, the payment processor will both check the details received by forwarding them to the respective card's issuing bank or card association for verification, and also carry out a series of anti-fraud measures against the transaction.
Additional parameters, including the card's country of issue and its previous payment history, are also used to gauge the probability of the transaction being approved.
Once the payment processor has received confirmation that the credit card details have been verified, the information is relayed back via the payment gateway to the merchant, who will then complete the payment transaction. If verification is denied by the card association, the payment processor will relay the information to the merchant, who will then decline the transaction.
View More On Wikipedia.org